The 216 Chevy six is what it is - regardless of vehicle. It was built from 1937 to 1953. The later 1955-1963 235 is a better motor, and is much easier to find. The 235 is a better deal in the long run because of the bearings and oiling system. The 216's had scoop type oiling and babbit bearings. The 235 has a pressurized oiling system. The stovebolt forum has a lot of info.

http://www.stovebolt.com/techtips/engine_swap_216.htm

Back in the day, I put a 235 Corvette 6 in my '52 Chevy, and it made a world of difference.