Further to what Bored and Stroked suggested, this is an old post of mine from last fall about low oil pressure on the poured bearing motor in my '36 pickup:
https://www.fordbarn.com/forum/showthread.php?t=317742
I put in high volume Melling M-15 pump from Speedway, USA made, with the late type oil pickup-a small modification needed to the oil pan to fit that pickup. I've run the truck about 1000 miles since then. Pressure remains 45psi at cold startup,40 psi running on the freeway in 75 degree ambient temp, and 10-15 psi at idle after a long freeway drive (with Valvoline VR-1 20/50) . I had concern about increased oil leakage at the rear main since there is no true oil seal there (just a labyrinth "seal") but none is evident. The motor runs nice and strong, as it always has. I realize this is considered a "Band-Aid" solution for increased bearing wear , but it certainly is cost effective and so far, so good-heck, for all I know, at age 76 this motor could outlast me. You might consider trying this as a relatively inexpensive step, along with purchasing the later motor in question. The oil pump swap is really pretty straightforward, and you can Plastigauge the mains and see where you're at in terms of wear.
Adam