273 302 318 340 build

I'd throw some sort of bore gauge in each hole and check for any of them being a lot bigger than the others, and look for how much taper and out-of-roundness and wear that you find. If you find .004"-.005" taper or more, it ain't gonna stay sealed up much longer, if it seals at all. I have found individual low compression engine bores worn .020+" and still have the compression check the same as the other cylinders...... oiling up through the rings can fool you big time with just a compression reading. But they won't run evenly that way and will be down on power bit time .....and going up in CR will just make any cylinder issues bigger. You gotta check it all if you are in there.....

Not too much crud underneath. That is good!

BTW< the bearings are 30 years old. Bearing materials start to get brittle and can start flaking off at about that age. I would be pulling the rod and main bearings for sure for sure; you have no way to know if one is flaking out or if is is badly scored and ready to let go. I assume you are going with the 302 heads and that will up the SCR and put more pressure on the bearings. It would be very unwise IMHO to not inspect the bearings at this time. Don't fret over the number of times those rod bolts have been used; these likely are 'virgin'.

Inspect the cam bearings (with a mirror for the bottom side) and if no flaking is seen, then maybe keep them in if you want to save the $$; they are a lot more forgiving than rod or main bearings. (But they can flake off too.)

How about pull the McCord head gaskets out of the box and look at them? Put a caliper on them to see if they are thick, like .050" or more. If you are lucky, these will be stock shim gaskets. I'll be straight-up with you: I think it is penny foolish to use thick head gaskets and expecting this engine to be a lot better for torque. The originals were shim gaskets around .022 thick; going with .050" thick head gaskets is just one more torque killer. Even with a smaller cam, you still need to fight for CR with those low CR pistons. 1121G gaskets are only $23 each; they ain't Cometics at $105 each!

Yeah, head work is not cheap, doggone it. But it is one of the 2 big keys to a solid running engine. (Good cylinder bores and rings and pistons being the other big key.)