I did the exact same thing back in '92.
Caps are matched to the block.
The short answer, you need a new block. Keep the cap as a suvinour of the old engine.
I was taking an engines class at a local community college back in Kansas. I drove it in. Just the typical signs of an older engine, used a bit of oil, little down on power. The whole calss saw me drive it in, no bad noises or anything else. We were all surprised when cap #2 was broken and had been for some time from the looks of the bearing wear. "never would have believed it ran as good as it did if I hadn't seen it myself" was one of the quotes I remember. I spent weeks searching a fix (this was before internet). Machine shop advise, searching everything I could. The aftermarket caps need line boring on top of just the fitting of the aftermarket caps. It just isn't worth it. I even found a cap in a junkyard, but fitting it to the block it was too far off to be machined out. The block is cast, machined for the caps with very loose tolerances. Doesn't matter since the factory will bore the crank bearings where they need to be. This puts the bearing saddle in completely random places on all the different main caps. Just like rods have matched caps to the rods, the main bearing cap has to be exactly right. The only realistic fix for my basic rebuild was find a different engine. The costs of saving what I had were all way overpriced for race parts that are a waste on a stock engine. And the bearing caps are not even the weak point in the 302 block, so you are not even addressing the weakest link.
