One thing I know for sure is that the position of the oil hole in the side of the lifter (not the cup) is important. These are different for the FE and the 429/460 engines. With the 429/460 lifters in the FE block, the oil hole in the lifter lines up with the oil gallery in the block. You do not want this, it will bleed a ton of oil out of the lifter at the cup, and when you are at lash the extra oil just floods into the valley. The FE lifters have that oil hole positioned so it does not line up with the oil gallery; the oil comes from the clearance volume between the lifter and the bore. This still provides plenty of oil to the pushrods, and doesn't bleed an excessive amount into the valley.
I had a set of 429 roller lifters once that looked like they would work in an FE block, so I tried them out. Pre-oiled with the intake off and saw tons of oil coming out the top of the lifters. I remember taking the pushrods out on one side, spinning the pump, and watching 8 streams of oil arc 4 feet over the engine, out of the lifter cups. I've got a picture of that somewhere; sure made a mess in the shop LOL.
Bottom line for you Royce is that if you have the right lifters in the block, you will not bleed an excessive amount of oil out of the lifter cups, even with solid pushrods and shaft oiling.