Bolt a trans and converter to it, and do a compression check. If it comes within 15 psi run it as is, just add a 4bbl and headers. If it has a bigger spread, oil the low cylinder and recheck. If the oil doesn't help much, it might be a valve. Or you could put a little air pressure in it through the spark plug hole and listen for the leak. If you hear it in a breather, not good. Hear it in the carb, pull the heads and lap the valves.
