OK, Hold the door! Post #77 shows an electric sending unit (to the left of the distributor) for your oil pressure gauge. Go buy a cheap mechanical gauge from one of the auto parts houses, take out that electric sending unit and slave in the mechanical gauge. I'll bet the current sending unit is way off! Do this before you do anything else on this motor and let us know what the idle psi reads with real mechanical gauge.
It is a mechanical gauge. On cold start will be around 60psi. Been idling for about ten minutes and is at about 13psi at idle 1k rpm in park. If I go to drive the idle goes to about 600 rpm and the pressure is at about 3psi