Have you ever noticed via a bunch of engine builds that oil galley passages don't always line up with gaskets and bearings? We will get arguments on this one, but oil holes that don't line up with bearings are due to core shift during block casting at the foundry or mis-aligned factory tooling when the block was machined. When you're selecting an engine block to start with, take a set of known good main bearings with you and check oil galley alignment. Any time oil galley alignment yields less than 50% of the passage, find another block. Mis-aligned oil galley passages are not your imagination nor are they always acceptable either. The harder you're going to run an engine, the more liberal oil galley passages need to be. If you've no choice but to use the block you have, chamfer the oil passages to improve flow to bearings. Main bearings have priority - always. Make sure they get plenty of oil.