While you're in there installing the Melling pump (great idea, BTW!) take a little time and inspect the rod bearings, including checking the oil clearance with Plastigauge. A new set of bearings will be cheap insurance, especially if the current ones are showing any wear, or if the oil clearance is over .002". Good luck!
Any oil pressure at all indicates the pump is supplying more oil than the bearings need. If not, the leakage from the bearings and other places would make the pressure zero. The idea of having oil pressure is to assure that everything that needs oil gets it- - - -with a bit to spare. Extremely high oil pressure is just wasted energy- - - -power used to drive the pump is power that can't be used to turn the transmission! Most "idiot light" switches turn the light on at 7 PSI, so a lot of folks without a pressure gauge have no idea how low their oil pressure really is at a hot idle.
Jerry
