Just for clarification,
The 216 was never used with an automatic or hydraulic lifters, Chevy borrowed its big truck 235 (in use since 1941) and put in bigger valves and hydraulic lifters for use with its new automatic in 1950.
Yes, the Rochester model B was used on the later 216's with a smaller bolt pattern, 2-3/4" wide, I think, and about 3" on the 235 and 261. While the manifold pattern did change, the pattern between the bowl and throttle body didn't, so swapping throttle bodies around is possible, I have done this before with no apparent ill effects, but I would recommend you use the proper parts together as intended. The bore diameters are all different between the 216, 235 and 261.
