This is my oil pump. The screw adjust the oil pressure that remains constant. There is also a fitting on the back that drives the cable drive fuel pump. This is driven by a pulley on the crankshaft. Four hoses go to the oil pan. There is no oil in the pan. It is stored in a 3 gal remote tank. The pump creates a vacuum in the crankcase to stop windage and help the rings seal better. The oil is on a thermostat like your radiator for quick warm up. You can also put an oil preheater on it if you want to start with warm oil. They say 80% of engine wear happens before your engine reaches temp. Hope that helps to explain it. Thank you for your time.
I had forgotten that, I seen those pictures earlier. Freeze plug down the hole would be fast and easy, or a machined plug with o-ring seal. Make the plug long, slot the bottom, drill a hole down the center, and thread a wedge to pull up into the slots with bolt down center. You would end up with plug and single bolt showing, o-ring seal and fingers wedging it into place.