Oil Pressure

I see people mentioning the oil line in this context all the time, so I'll say it again.

Oil in the line is a by product of running and shutting down (heating and cooling)
Not having any oil in the line means nothing because it is a dead ended system at the gauge and oil in the line or not makes ZERO difference.
The gauge still reads the pressure.

I get that, the column of air inside the tube acts as a pushrod to transfer the pressure that is present in the engine to push the dial on the gauge

however, when reading the OP, it seemed to me the gauge was hooked up and reading zero PSI


Take spark plugs out . Hook up oil pressure line, turn it over with starter. You should have pressure.

I would suggest against that

on my 360 I get 70 PSI with a priming rod and a regular volume pump
he should be seeing SOME with that high volume pump on there

it has to be going somewhere...unless he is spinning it counter clock wise