D15 149 Gas No Oil Pressure

A while back my D15 seized the engine. The rear main bearing was a mess and #2 and #3 journals on the crank shaft where deeply scored and where already turn the max 5 years ago when I rebuilt this motor. I looked like the crank shaft had gotten hot from lack of oil flow but the oil pressure gauge was stuck so I don't know what the pressure was. There was good coolant flow in the motor.

New parts

crank shaft

4 sleeves and pistons Reliance over bore kit

oil pump rebuild kit

electronic ignition (engine always had a skip under heavy load)

alternator (converted tractor to 12 volt negative ground to solve charging headaches.)

Bearing and gaskets of course

oil pressure gauge

tempiture gauge

voltage gauge

Resembled the motor and while adjusting the valves found there was no oil flow. Never thought to check the pressure. Shut down the engine but it was too late I damage the #1 piston seized the wrist pin and damaged the bearing. Everything else looks ok in the engine. I checked all the oil passages with air pressure and they are clear. Check the oil pump and can find nothing wrong with it. Checked the cam shaft and the drive pin for the oil pump is not damaged. But the oil pump never picked up any oil the oil filter housing was dry. I am totally stumped as to why my oil pump which looks perfectly fine with a new rebuild kit isn't pumping oil.