There is a difference in the manifolds for the 216 and (1954 and later) 235 6's. The carb mounting flange bolt spacing, center to center, is 2-13/16 on a 216 intake and 2-15/16 on a (54 and later) 235 intake, so you have to watch it when acquiring a spare carb or buying a dual intake. The studs on a 216 exhaust manifold that bolt the exhaust and intake together also has a different spacing from a (54 and later) 235 exhaust manifold; making them it unique as well.
Chevrolet did build a 235 prior to 1954. They started building these in 1941 -> (
http://1954advance-design.com/Stovebolt-engine/casting-numbers.html - See next right most column) I have read that these low pressure 235's were mostly put into the big trucks and that there are very few parts on them that will interchange with a 54 and later 235's. They VERY likely shared the same manifold with the 216. I am not sure but I am willing to bet that they looked the same as a 216 with the full cover on the right side of the engine. Perhaps someone could provide some clarity on this point. Check the casting numbers to be sure on the link above. Really nothing is interchangeable between the 216 and (54 and later) 235. Well, the flywheels are said to be swappable, and you can put a 216 valve cover on a 235.
Hope this helps.
Keep on truckin'
Walt Williams
