The oil passage that goes between the #1 main brg and #1 cam brg intersects the passage that goes from the oil pump to the main oil galley. The intersection is about half way between the main brg and cam brg. You would probably only have to drill from the main brg up to the point where they intersect. I would think that the #1 main would have plenty of pressure as it is. Plus that passage only feeds one rod brg, not two like #'s 2,3,and 4.