Are the bearings black from the coating or because they were not well lubed?

I am not a fan of drilling all the passages way bigger, it means longer on a cold start to fill em all up and with 40-80 PSI should give plenty of volume to the crank through the factory passages, maybe radius some of the sharp edges, a crank scraper, a couple extra oil holes in the filter plate, full groove mains if your gonna turn a lot of RPM and call it good, too many people way over think the oiling on a 6000 or 7000 RPM SB.

Like others have mentioned check for a passage bleeding internally, it may not have gone through at first then after running a little it popped through a thin spot.