OK there's your problem
Take the cam cover off and retrace your steps by pulling the cam plate.
I suggest the following:
1 Put the stock relief spring back in
2 Change to a Baisley relief spool, be sure the spool works freely in the bore no hangups, the part has a better finish and will truely seal for better oil pressure and less bleed back to inlet side
3 Check the oil pump gears and housing for wear and proper assembly order, replace as required with stock parts
4 Mike the cam plate bushing and check for wear, replace as required with stock parts (this part will not be worn unless the crank has sizeable runout)
5 Check the crank runout, both sides pinion and sprocket, repair if required (IMO equal to or over .006" runout)
6 Reassemble cam plate assy.with a new OEM oil pump case oring 11293 and lube it with white litium grease or Dow Corning #55 Oring lubricant
7 Use new cam plate orings 11301 (2)
8 Align the oil pump following the service manual method by turning the motor, with lifters out you can use the starter ( I do but there may be some pushback from others on this method) no tapered pins required and this method puts the pump where it wants to be not where the bolt holes are in relation to the scavenge spigot
9. Reassemble and check oil level, leave 1/2 qt low cold
Ride and recheck for sumping. 1-4oz is normal on these late models.