A quick fix that can improve oil pressure without a great deal of expense or labor time would be changing the connecting rod bearings "in the frame". Just drop the oil pan and swap out the bearing shells one at a time. No need pull the engine, or mess with the main bearings. Just be sure the replacement bearings are the proper size. I usually "shoeshine" the crankshaft journals with a long strip of cloth-backed sandpaper, followed by a thorough cleanup, to smooth out any roughness on the journals.
Jerry
