diff --git a/ndsl/stencils/testing/serialbox_to_netcdf.py b/ndsl/stencils/testing/serialbox_to_netcdf.py
index 11814fff..a29139c5 100644
--- a/ndsl/stencils/testing/serialbox_to_netcdf.py
+++ b/ndsl/stencils/testing/serialbox_to_netcdf.py
@@ -32,6 +32,13 @@ def get_parser():
         type=str,
         help="[Optional] Give the name of the data, will default to Generator_rankX",
     )
+    parser.add_argument(
+        "-m",
+        "--merge",
+        action="store_true",
+        default=False,
+        help="merges datastreams blocked into separate savepoints",
+    )
     return parser
 
 
@@ -58,7 +65,12 @@ def get_serializer(data_path: str, rank: int, data_name: Optional[str] = None):
     return serialbox.Serializer(serialbox.OpenModeKind.Read, data_path, name)
 
 
-def main(data_path: str, output_path: str, data_name: Optional[str] = None):
+def main(
+    data_path: str,
+    output_path: str,
+    merge_blocks: bool,
+    data_name: Optional[str] = None,
+):
     os.makedirs(output_path, exist_ok=True)
     namelist_filename_in = os.path.join(data_path, "input.nml")
 
@@ -69,8 +81,21 @@ def main(data_path: str, output_path: str, data_name: Optional[str] = None):
     if namelist_filename_out != namelist_filename_in:
         shutil.copyfile(os.path.join(data_path, "input.nml"), namelist_filename_out)
     namelist = f90nml.read(namelist_filename_out)
-    total_ranks = (
-        6 * namelist["fv_core_nml"]["layout"][0] * namelist["fv_core_nml"]["layout"][1]
+    if namelist["fv_core_nml"]["grid_type"] <= 3:
+        total_ranks = (
+            6
+            * namelist["fv_core_nml"]["layout"][0]
+            * namelist["fv_core_nml"]["layout"][1]
+        )
+    else:
+        total_ranks = (
+            namelist["fv_core_nml"]["layout"][0] * namelist["fv_core_nml"]["layout"][1]
+        )
+    nx = int(
+        (namelist["fv_core_nml"]["npx"] - 1) / (namelist["fv_core_nml"]["layout"][0])
+    )
+    ny = int(
+        (namelist["fv_core_nml"]["npy"] - 1) / (namelist["fv_core_nml"]["layout"][1])
     )
 
     # all ranks have the same names, just look at first one
@@ -96,8 +121,30 @@ def main(data_path: str, output_path: str, data_name: Optional[str] = None):
                     rank_data[name].append(
                         read_serialized_data(serializer, savepoint, name)
                     )
+                nblocks = len(rank_data[name])
+                if merge_blocks and len(rank_data[name]) > 1:
+                    full_data = np.array(rank_data[name])
+                    if len(full_data.shape) > 1:
+                        if nx * ny == full_data.shape[0] * full_data.shape[1]:
+                            # If we have an (i, x) array from each block reshape it
+                            new_shape = (nx, ny) + full_data.shape[2:]
+                            full_data = full_data.reshape(new_shape)
+                        else:
+                            # We have one array for all blocks
+                            # could be a k-array or something else, so we take one copy
+                            # TODO: is there a decent check for this?
+                            full_data = full_data[0]
+                    elif len(full_data.shape) == 1:
+                        # if it's a scalar from each block then just take one
+                        full_data = full_data[0]
+                    else:
+                        raise IndexError(f"{name} data appears to be empty")
+                    rank_data[name] = [full_data]
             rank_list.append(rank_data)
-        n_savepoints = len(savepoints)  # checking from last rank is fine
+        if merge_blocks:
+            n_savepoints = 1
+        else:
+            n_savepoints = len(savepoints)  # checking from last rank is fine
         data_vars = {}
         if n_savepoints > 0:
             encoding = {}
@@ -166,7 +213,10 @@ def entry_point():
     parser = get_parser()
     args = parser.parse_args()
     main(
-        data_path=args.data_path, output_path=args.output_path, data_name=args.data_name
+        data_path=args.data_path,
+        output_path=args.output_path,
+        merge_blocks=args.merge,
+        data_name=args.data_name,
     )