PLEASE don't throw a belly button engine in there!
I have a '54, with 324 engine. I have pulled this engine, and it sits in the corner of my shop, awaiting a full resto, In the meanwhile I will use a 455 Olds engine.
You have a classic car, don't use a common old chev engine, My opinion, is it'll loose a lot of character.
It's your car, and your choice, but you asked for opinions.(?)
Good luck either way, & let us know what you decide to do.