If I repeat what somebody else has said in some other post(s) then please erase or delete this Post.

Before I built my 360 I was Talking to American Performance in Florida and I talked to Barry out in West Virginia (Who strictly deals with AMC's and some others) they said... "where the oil drains through the heads and back into the sump/oil pan this passage way can be enlarged up to an 1/8" to improve oil flow back into the pan... resulting to less pooling in the heads"... (But they recommended that you should check the thickness of the castings before drilling in-order to be safe and to get the most out of it) They also mentioned checking all of the holes that were drilled for oiling the mains and mostly the rear because there are cases where only the tip of the drill has penetrated into the passage-way and not the full flutes of the drill causing a restriction or oil starvation, (Mostly to the rear mains... etc etc).
I'm sure this is already known, I just figured I'd toss out what was said to me.