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.
That's why you use a HV pump. You can't get enough oil to these things. Open up the oil galleries, control all the internal leaks and get as much oil as fast as you can out of the pump and to the crank.
