Yes that would be a variable. But as I posted earlier about using a high volume pump, unless you are after every last horse power from your build, extra volume and pressure is not going to hurt you.
Having not enough will.
Same with drilling the block passages larger. It ain't gonna hurt, and as you have said, at high rpm you may need it.
But the suction side is different. If the pump is into bypass and recirculating oil inside the pump, there would not even be any flow inside the pickup tube until the bypass closes again. I am thinking
That the eBay pickup and the milodon, even though they still only use the stock size thread, but with a larger diameter tube there would be a Venturi effect that would still offer better suction.
Now if you want an interesting read, Ryer Morrison says pickups don,t suck at all. He claims the oil is displaced into the pickup by the oil level in the pan. It is forced in or something to that effect. Lol
