New to me 73 duster 340

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.