Actually I always prefill the oil filters.
I have removed the plate style oil cooler and about 5 feet worth of line. Now I am running only the dual filter assembly with about 4.5 feet of hose.
I started the car and slowly added oil until the gauge was moving in the right direction when revving. I used a mechanical gauge with a magnet mount so it was right there in the engine bay, and I could monitor it while filling.
I needed to add a little over a quart to the sump, on top of the 2 quarts needed to prefill the filters. So that works out to about 7.5-8 quarts total with the added lines and filters (it's a 5 qt pan with windage tray).
Currently at operating temp I am running about 25-30 psi at idle and about 60psi at 2,000 rpms. Currently I am still using 10W-30 Amsoil.