For those of you who may have followed the thread, or contributed suggestions, here's the end of my high oil pressure story.  I went out to California Monday and called on Ron Monson at the Performance Engines shop.  Although I'd scratched my head over this apparently simple mechanism (the oil pressure regulator), and had showed it to 2 or 3 A&P's, Ron almost immediately spotted what we all had missed.
   The oil pressure regulator consists of a cylinder screwed into the oil pump housing, inside of which is a spring, a piston, a plunger rod, and a cap washer.  The cap washer has a machined groove that helps seat it on top of the spring.  The cap washer was too big.  That simple.  We pulled some others out of his parts bin, and the one I had was about 0.040" bigger than any of the rest.  (Thanks, TCM!)  There was almost no clearance between the cap washer and the cylinder.  In fact, the cap washer was not able to go all the way up to the top of the cylinder.  Furthermore, it was apparently binding on the cylinder walls, as evidenced by some faint ridges that you could feel with a finger.  So, instead of allowing the piston to move back and forth and regulate the oil pressure, the cap washer was apparently sticking part way down in the cylinder, applying too much pressure to the piston.
   All's back together, and after a couple of tweaks of the adjusting screw, I now have 57psi oil pressure, steady as a rock.

   It's the little things . . .

Jim Cameron
Legacy N132X
Boerne, TX