I have to say, that I have never had a main bearing hole that badly out of alignment, that said, if that block was used in an engine that was first built 50 years ago, I guess an adequate amount of oil must have gotten to where it was needed. For many years, I used to always take a die grinder and blend the oil holes to make them line up perfectly to the hole in the bearing shells. I stopped doing that over 10 years ago, after one of the 428 blocks in my Fairmont drag car split the main webbing on the 2nd & 4th bulkheads between the cam and crankshaft bores. The cracks went directly through the oil feed holes, right where I had chambered the holes. Now, maybe the cracks would have happened even if I never had touched the holes with a grinder, I don`t know. I did not really remove very much material, but it cracked right there. I remember years ago, hearing about guys that actually drilled the oil holes in the main webs larger than stock. Considering how narrow the web bulkheads are, that sure sounds like a bad plan.