Do you still have the 265 engine?
I have a 1955 Belair with a engine stored too long. Knocking on bottom end.
Rather than rebuild, would buy a rebuild or rngine with no problems.
You will seriously devalue your car if you use a non original engine! Rebuild what you have. If you want to ruin the car use any old 350 Chevy engine.
Yes! If the "55 BelAir is really nice, keep it as original as possible; including the original engine, in original configuration. If you can't do that, you could use a period engine, 265, 283, or even a 348, that will be a bolt-in. Or replace with a newer, really big mouse motor..... I had a "57 BelAir an put in the drive train from a "60 dual-quad Corvette. Looked really nice.