Per your question, we're working on a 1950 GMC 3/4 ton truck. Again, I defer to the experts but it seems the Chevrolet 235 is marginally shorter than a GMC engine. Not much, but enough to warrant the fabrication of engine mounts that will eventually support the rear of the engine.
OK, that part makes sense, but the part about the difference between early 235 vs '53 235 does not. They mount the same way.
One other point is that a '53 w/Powerglide engine is actually the first version of the more modernized 235. It is essentially the same as a '54 235.
Engines which came '55 and later would actually cause you more work, as they came with lower mounted watepumps which causes the fan to be too low on the radiator.
