I would suggest removing the distributor and spinning the oil pump with a 1/2" drill motor to see if oil pressure develops. Use a piece of 1/2" round rod with a flat ground into the end of it, or a large-bladed screwdriver bit cut off and ground to fit the slot in the pump drive. Spin the pump clockwise and watch the pressure gauge. I'd expect to see at least 30 PSI with that procedure, and 40 or more would not be unusual. As the engine warms up and the oil thins, the pressure will drop. 15-30 PSI at a hot idle would be normal for a relatively new engine or a recent rebuild. Max pressure at cruise RPM on a hot engine will depend on the tension of the oil pump relief spring.
Jerry

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