diff --git a/flopy4/mf6/codec/__init__.py b/flopy4/mf6/codec/__init__.py
index c5f3faba..34f14966 100644
--- a/flopy4/mf6/codec/__init__.py
+++ b/flopy4/mf6/codec/__init__.py
@@ -14,14 +14,14 @@
     unstructure_component,
     unstructure_oc,
 )
-from flopy4.mf6.spec import get_blocks
 
 _JINJA_ENV = Environment(
     loader=PackageLoader("flopy4.mf6"),
     trim_blocks=True,
     lstrip_blocks=True,
 )
-_JINJA_ENV.filters["blocks"] = get_blocks
+_JINJA_ENV.filters["dict_blocks"] = filters.dict_blocks
+_JINJA_ENV.filters["list_blocks"] = filters.list_blocks
 _JINJA_ENV.filters["field_type"] = filters.field_type
 _JINJA_ENV.filters["field_value"] = filters.field_value
 _JINJA_ENV.filters["array_how"] = filters.array_how
diff --git a/flopy4/mf6/codec/converter.py b/flopy4/mf6/codec/converter.py
index 5ff838bf..b614d713 100644
--- a/flopy4/mf6/codec/converter.py
+++ b/flopy4/mf6/codec/converter.py
@@ -146,52 +146,33 @@ def unstructure_component(value: Component) -> dict[str, Any]:
 def unstructure_oc(value: Any) -> dict[str, Any]:
     data = xattree.asdict(value)
     for block_name, block in get_blocks(value.dfn).items():
-        if block_name == "perioddata":
-            # Unstructure all four arrays
-            save_head = unstructure_array(data.get("save_head", {}))
-            save_budget = unstructure_array(data.get("save_budget", {}))
-            print_head = unstructure_array(data.get("print_head", {}))
-            print_budget = unstructure_array(data.get("print_budget", {}))
-
-            # Collect all unique periods
+        if block_name == "period":
+            # Dynamically collect all recarray fields in perioddata block
+            array_fields = []
+            for field_name, field in block.items():
+                # Try to split field_name into action and kind, e.g. save_head -> ("save", "head")
+                action, rtype = field_name.split("_")
+                array_fields.append((action, rtype, field_name))
+
+            # Unstructure all arrays and collect all unique periods
+            arrays = {}
             all_periods = set()  # type: ignore
-            for d in (save_head, save_budget, print_head, print_budget):
-                if isinstance(d, dict):
-                    all_periods.update(d.keys())
+            for action, rtype, field_name in array_fields:
+                arr = unstructure_array(data.get(field_name, {}))
+                arrays[(action, rtype)] = arr
+                if isinstance(arr, dict):
+                    all_periods.update(arr.keys())
             all_periods = sorted(all_periods)  # type: ignore
 
-            saverecord = {}  # type: ignore
-            printrecord = {}  # type: ignore
+            perioddata = {}  # type: ignore
             for kper in all_periods:
-                # Save head
-                if kper in save_head:
-                    v = save_head[kper]
-                    if kper not in saverecord:
-                        saverecord[kper] = []
-                    saverecord[kper].append({"action": "save", "type": "head", "ocsetting": v})
-                # Save budget
-                if kper in save_budget:
-                    v = save_budget[kper]
-                    if kper not in saverecord:
-                        saverecord[kper] = []
-                    saverecord[kper].append({"action": "save", "type": "budget", "ocsetting": v})
-                # Print head
-                if kper in print_head:
-                    v = print_head[kper]
-                    if kper not in printrecord:
-                        printrecord[kper] = []
-                    printrecord[kper].append({"action": "print", "type": "head", "ocsetting": v})
-                # Print budget
-                if kper in print_budget:
-                    v = print_budget[kper]
-                    if kper not in printrecord:
-                        printrecord[kper] = []
-                    printrecord[kper].append({"action": "print", "type": "budget", "ocsetting": v})
-
-            data["saverecord"] = saverecord
-            data["printrecord"] = printrecord
-            data["save"] = "save"
-            data["print"] = "print"
+                for (action, rtype), arr in arrays.items():
+                    if kper in arr:
+                        if kper not in perioddata:
+                            perioddata[kper] = []
+                        perioddata[kper].append((action, rtype, arr[kper]))
+
+            data["period"] = perioddata
         else:
             for field_name, field in block.items():
                 # unstructure arrays destined for list-based input
diff --git a/flopy4/mf6/filters.py b/flopy4/mf6/filters.py
index 96cc5daf..5d5f0739 100644
--- a/flopy4/mf6/filters.py
+++ b/flopy4/mf6/filters.py
@@ -4,9 +4,41 @@
 import numpy as np
 import xarray as xr
 from jinja2 import pass_context
-from modflow_devtools.dfn import Field
+from modflow_devtools.dfn import Dfn, Field
 from numpy.typing import NDArray
 
+from flopy4.mf6.spec import get_blocks
+
+
+def _is_list_block(block: dict) -> bool:
+    return (
+        len(block) == 1
+        and (field := next(iter(block.values())))["type"] == "recarray"
+        and field["reader"] != "readarray"
+    ) or (all(f["type"] == "recarray" and f["reader"] != "readarray" for f in block.values()))
+
+
+def dict_blocks(dfn: Dfn) -> dict:
+    """
+    Get dictionary blocks from an MF6 input definition. A
+    dictionary block is a standard block which can contain
+    one or more fields, as opposed to a list block, which
+    may only contain one recarray field, using list input.
+    """
+    x = {
+        block_name: block
+        for block_name, block in get_blocks(dfn).items()
+        if not _is_list_block(block)
+    }
+    return x
+
+
+def list_blocks(dfn: Dfn) -> dict:
+    x = {
+        block_name: block for block_name, block in get_blocks(dfn).items() if _is_list_block(block)
+    }
+    return x
+
 
 def field_type(field: Field) -> str:
     """
diff --git a/flopy4/mf6/gwf/oc.py b/flopy4/mf6/gwf/oc.py
index ef600320..6bcae76a 100644
--- a/flopy4/mf6/gwf/oc.py
+++ b/flopy4/mf6/gwf/oc.py
@@ -3,7 +3,7 @@
 
 import numpy as np
 from attrs import Converter, define
-from modflow_devtools.dfn import Dfn, Field
+from modflow_devtools.dfn import Field
 from numpy.typing import NDArray
 from xattree import xattree
 
@@ -111,7 +111,7 @@ class Period:
     format: Optional[Format] = field(block="options", default=None, init=False)
     save_head: Optional[NDArray[np.object_]] = array(
         Steps,
-        block="perioddata",
+        block="period",
         default="all",
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
@@ -119,7 +119,7 @@ class Period:
     )
     save_budget: Optional[NDArray[np.object_]] = array(
         Steps,
-        block="perioddata",
+        block="period",
         default="all",
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
@@ -127,7 +127,7 @@ class Period:
     )
     print_head: Optional[NDArray[np.object_]] = array(
         Steps,
-        block="perioddata",
+        block="period",
         default="all",
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
@@ -135,19 +135,20 @@ class Period:
     )
     print_budget: Optional[NDArray[np.object_]] = array(
         Steps,
-        block="perioddata",
+        block="period",
         default="all",
         dims=("nper",),
         converter=Converter(structure_array, takes_self=True, takes_field=True),
         reader="urword",
     )
 
-    @classmethod
-    def get_dfn(cls) -> Dfn:
-        """Generate the component's MODFLOW 6 definition."""
-        dfn = super().get_dfn()
-        for field_name in list(dfn["perioddata"].keys()):
-            dfn["perioddata"].pop(field_name)
-        dfn["perioddata"]["saverecord"] = _oc_action_field("save")
-        dfn["perioddata"]["printrecord"] = _oc_action_field("print")
-        return dfn
+    # original DFN
+    # @classmethod
+    # def get_dfn(cls) -> Dfn:
+    #     """Generate the component's MODFLOW 6 definition."""
+    #     dfn = super().get_dfn()
+    #     for field_name in list(dfn["perioddata"].keys()):
+    #         dfn["perioddata"].pop(field_name)
+    #     dfn["perioddata"]["saverecord"] = _oc_action_field("save")
+    #     dfn["perioddata"]["printrecord"] = _oc_action_field("print")
+    #     return dfn
diff --git a/flopy4/mf6/spec.py b/flopy4/mf6/spec.py
index 63bcb40e..4a56fe1b 100644
--- a/flopy4/mf6/spec.py
+++ b/flopy4/mf6/spec.py
@@ -134,7 +134,8 @@ def block_sort_key(item: tuple[str, dict]) -> int:
         return 2
     elif k == "packagedata":
         return 3
-    elif k == "perioddata":
+    elif "period" in k:
+        # some packages have block "period", some have "perioddata"
         return 4
     else:
         return 5
diff --git a/flopy4/mf6/templates/blocks.jinja b/flopy4/mf6/templates/blocks.jinja
index 0acd2920..07392dac 100644
--- a/flopy4/mf6/templates/blocks.jinja
+++ b/flopy4/mf6/templates/blocks.jinja
@@ -1,5 +1,5 @@
 {% import 'macros.jinja' as macros with context %}
-{% for block_name, block_ in (dfn|blocks).items() %}
+{% for block_name, block_ in (dfn|dict_blocks).items() %}
 BEGIN {{ block_name.upper() }}
 {% for field in block_.values() -%}
 {{ macros.field(field) }}
@@ -7,3 +7,7 @@ BEGIN {{ block_name.upper() }}
 END {{ block_name.upper() }}
 
 {% endfor %}
+
+{% for block_name, block_ in (dfn|list_blocks).items() -%}
+{{ macros.list(block_name, block_) }}
+{%- endfor%}
diff --git a/flopy4/mf6/templates/macros.jinja b/flopy4/mf6/templates/macros.jinja
index baa3477f..86bf07ff 100644
--- a/flopy4/mf6/templates/macros.jinja
+++ b/flopy4/mf6/templates/macros.jinja
@@ -7,7 +7,7 @@
 {% elif type == 'keystring' %}
 {{ keystring(f) }}
 {% elif type == 'recarray' %}
-{{ recarray(f) }}
+{{ recarray(f, how=f|array_how) }}
 {% endif %}
 {% endmacro %}
 
@@ -29,16 +29,9 @@
 {%- endfor %}
 {% endmacro %}
 
-{% macro recarray(f) %}
+{% macro recarray(f, how="internal") %}
+{% set name = f.name %}
 {% set value = f|field_value %}
-{% if f.reader != 'readarray' %}
-{{ list(f) }}
-{% else %}
-{{ array(f.name, value, how=f|array_how) }}
-{% endif %}
-{% endmacro %}
-
-{% macro array(name, value, how="internal") %}
 {{ name.upper() }}{% if "layered" in how %} LAYERED{% endif %}
 
 {% if how == "constant" %}
@@ -57,9 +50,28 @@ OPEN/CLOSE {{ value }}
 {% endif %}
 {% endmacro %}
 
-{% macro list(f) %}
-{{ f }}
-{% for item in f.children.values() %}
-{{ field(item) }}
+{% macro list(block_name, block) %}
+{#
+from mf6's perspective, a list block (e.g. period data)
+always has just one variable, whose elements might be
+records or unions. where we spin those out into arrays
+for each individual leaf field to fit the xarray data
+model, we have to combine them back here.
+
+this macro receives the block definition. from that
+it looks up the value of the one variable with the
+same name as the block, which custom converter has
+made sure exists in a sparse dict representation of
+an array. we need to spin this out into a block for
+each stress period.
+#}
+{% set dict = data[block_name] %}
+{% for kper, value in dict.items() %}
+BEGIN {{ block_name.upper() }} {{ kper }}
+{% for line in value %}
+{{ line|join(" ")|upper }}
+{% endfor %}
+END {{ block_name.upper() }} {{ kper }}
+
 {% endfor %}
 {% endmacro %}
diff --git a/test/test_codec.py b/test/test_codec.py
index bc5b64fc..b365bde7 100644
--- a/test/test_codec.py
+++ b/test/test_codec.py
@@ -21,7 +21,6 @@ def test_dumps_ic():
     assert result
 
 
-@pytest.mark.xfail(reason="TODO period block unstructuring")
 def test_dumps_oc():
     from flopy4.mf6.gwf import Oc