So I don't THINK I am wrong here, but Chevy made the post 53 235 and then modified mostly externals for different applications. ANY 235 or 261 engine from 54-62 will be just fine. If you want hydraulic lifters, your engine shop will provide them for you for any block. If you want the acorn nuts on top of the engine to make it look like a 216 authentic year, just buy the kit or do it yourself. You are over thinking it.
You should have whatever engine you get rebuilt.. if you do it yourself you need the block cleaned and machined and the head machined as well. If you want a different cam, whatever. that is the time. Hope this helps! Next is important!
ANY time you purchase a 236 or 261 from anyone you run the risk of the cylinders already machined to 6 thousands over (the max) and makes it worthless. So be careful that you don't pay for any unknown engine more than you are willing to gamble with. Or make a deal with the seller that the engine shop needs to approve its rebuilding capability before purchase. I have 5 235's and a 261 and I wouldn't sell any of them to anyone because I am not sure how much rebuilding has been done, how many of the heads are good, etc. Just buyer beware.
Couple of errors. It will make a difference on hydraulic or solid lifters on '54-'56 blocks, the oiling systems are different. The Hydraulic lifter block can run either version, but the solid lifter block can only run solids. After '57, that is no longer an issue.
The max overbore is 60 thousands (.060), rather than 6 thousands (.006). even then, I've been told by a reputable machinist that the 236/261 can safely go 80 thousands (.080). Note, TRW does make .080 pistons and Sealed Power has the matching rings for this engine.
