Rebuilt Engine, Super Low Oil Pressure :(

TrailBeast said
GPM normally, and a good solid stream.
As in if you started it and walked around to see it should have made a huge multi quart puddle.
Do you remember tightening the oil pump down?
Or happen to leave a rag in it?

It happens.

i assumed he was just cranking so there wouldn't be much.

and i totally forgot about the pressure spring! could be stuck or missing.

as to your question there is a NPT plug front and read for the main oil galley.