I have now looked through the FAQ again, and my engine does seem to fit the criteria for being a later 235. ie 4 screws holding the cam cover on, shorter side cover which doesnt go up to the spark plugs.

numbers I have off the engine.

B48 348 850
0225 I4I F54M <- stamped in just next to dizzy
G836 848 GM26
A154

many thanks in advance.