I believe this probably correct and that this modification (oil holes in the lifter galley) will actually have a negative effect. I want the oil running to the ends of the block and not down on the crankshaft adding to the windage problem.
Drilling out the main bearing feeds is probably not necessary on the Magnum block as the #2 & #4 cam bearings are not supplying oil to any rocker shafts.
I do recommend the main cap modification suggested.