My 100 has "suffered" from low hot oil pressure since I put it together thirty years ago. On a hot engine at 2500 rpm or so, it runs about 25 psi, give or take a few. At idle it drops to below 10. I use 20W 50 oil in it most of the time.
My engine has an original gear type pump that I checked for wear and it measured up as I recall. The main and rod bearings were new on this car 30 years ago, with nominal clearances on a newly ground crank. The rocker shaft is in very good shape.
I have driven this car thousands of miles in very hot weather with this low oil pressure with no problems at all that I can see. I am sure that a higher capacity pump would increase the oil pressure, but is it necessary? Remember that higher flow of oil through the bearings will also increase runoff from the bearings, especially the rear main which tends to leak like crazy from a 100. Ditto for flow up into the head, which has limited pathways for return back into the case.
I know it feels good to see 50 psi on that gage all the time, but is it really necessary? I would be reluctant to fool with a high capacity pump unless I was racing or had some sort of lubrication problem that was known to be caused by low oil flow.
Good luck!
Bill.