A 216 carburetor on a 235 engine will run slightly rich. Higher air velocity for any specific RPM. If the Rochester B fits the 216 intake manifold, its a 216 carburetor. 235 carbs won't bolt on. Unless you swap to the right intake/exhaust manifold assembly and a properly calibrated carb, there's not much else you can do about the situation.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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