Re: block question
To answer your question, no. They are the same block.
Loosing compression, what's causing it? Do you know? If its something as simple as broken ring land, find out how bad the cylinder walls are. They might still have the cross hatching still and won't need a hone/bore. If that's the case you only need new bearings, pistons and rings to put it back to running. Or you can upgrade rods while your in there. And do a 4 bolt main.
Don't missunderstand my simple answers. This can be a simple, very fast rebuild. Or it can cost you thousands if you get carried away.
You need to sit down and figure out what you want in tbr future with your truck. Because if you were wanting a rebuild to make it stronger and faster. You have the chance to do it once and not 3 times. If you just want a mostly stock truck. Then just fix what's wrong. Jmo