I had a 383 stroker years ago that ate a rod bearing on the dyno. When I tore it down I found a main oil passage that was partially blocked. When we built the engine we just never checked the oil feeds but now I always double check them. I don't think they need to be huge but they should be open. I have some extra long 17/64 reamers that I run down thru the holes. Sometimes one of the holes will make a big pile of chips so that tells you that it was pretty tight.