Gravely Model L: oil pump: high pressure dry sump: problems

I am working on my 1977 Gravely L: Super Convertible. That has been sitting for years. Did the basics changed oil, new spark plug, new air filter, rebuilt 12 volt starter motor. Did not change the oil filter. Got the magneto sparking so it will start: BUT, NO OIL PRESSURE. Removed the old gauge: started again but still no flow. The engine sounded good during the brief run times.

Assuming an supply restriction or something simple, I looked at on line manuals. Did not find much. The diagrams were are a bit confusing: the 1953 parts list: older wet-sump systems indicates a oil-strainer body tube part: L822. The 7.6 parts list: dry sump systems indicates a transmission screen part: 10146A1. Anyone sell or use a replacement screen?

Next: I removed the external 5:16 supply tube to the oil pump. Oil did ooze out onto the floor when I removed it BUT it also did not exactly pour out even when I tilted the machine backward. I blew it backward with compressed air. Iit bubbled inside the transmission but the flow did not increase much, if any. Does it need an internal flushing cleaning with kerosene or something? Is it be best or necessary to remove the axle housing for accessibility?

Then: I removed the oil pump cover. Every thing appeared fine: just no oil just dry. How or Why is the pump-housing completely dry?. Will that special and-small Allen-head bottom-cap-bolt actually torque to 80 inch pounds. I had to take it off with vice grips; it was much tighter than all the others?

Since it almost appears to be gravity flow or almost gravity flow from the transmission pick-up to the oil pump why will it not self prime and siphon? Should I over-fill one quart or so? Does the system need initial priming either by pressure or vacuum to initialize the siphon possibly from the pressure gauge connection?

Am I overlooking something obvious?

NOTE: I once removed a low pressure oil strainer body tube from a spare parts transmission with no motor. It was rusty and really gunky but removed easily.

I suggest you clean the thing out as best you can with diesel. Make sure the lines are clear and not crimped, the filter will pass oil ( I got one once with no holes on the interior- no way oil could pass!), make sure the little key in the oil pump gear isn't sheared and that you have the proper gasket on the cover. That cover gasket is very thin, make sure you have a correct one. Make sure the pump is turning with the engine too. You can prime the lines to a certain extent and make sure theres oil of some kind in the pump when you put the cover back on. You can pull the spark plug and turn the engine over (especially if electric start) to see if oil pressure builds before starting. If none of that works it possible the pump clearances are simply worn and too large to allow it to pump.