Yes, it's quite possible for the scavenge side to work but not the feed.
They are in effect two separate pumps driven by the same shaft. The feed gears are driven by wither a split pin or a solid pin. Both gave been used. The scavenge side uses a half moon key.
So, either can fail and not turn the gears.
The feed side feeds oil to the engine through two different routes. One is a an end feed into the crankshaft. The other is through ddrillings in the cam cover and up through the cases for the feed to the rockers.
It's quite possible that the passage to the top end is blocked. The wrong gasket or "gasket goo" on the cam cover could cause that problem.
here's your problem. If it's the cam cover pulling that will easier - but - it night not be the problem.
Pilling the pimp is a lot harder and it might not be the problem.
If the feed pump IS working then you would be getting oil to the bottom end. If you kick long enough and the oil stops returning to the oil tank then the feed isn't working and the pump has to come off.
If your engine has a sump plug you could try draining the sump completely and then kicking the engine over long enough to start dripping out the drain hole. If it never starts dripping the pump ain't working.