1941 and later 216 heads are scalloped down the drivers side around the head bolts, earlier are straight.
I have seen the earlier head used on a later engine without a heating problem.
When I hear of a heating problem and everything has been checked out, I think about ignition timing. Retarded ignition ignition timing can cause overheating.
I have also seen where the lower radiator hose collapses when warmed up.
Lower radiator hoses should have some sort of wire coil in them to prevent collapse.
