I have had no problem priming my 1960 261 full-flow system with a "sawed-off" large screwdriver attached to a power drill.
I also have had no problem priming that same engine using a distributor with the drive gear removed - it was easily rotated with a power drill. (my preferred method - I'll post a photo if I have find that oil-priming-distributor))
Either way, you are spinning the sealed oil-pump internal-gear.
Either way, you should get oil flow/movement through all of the internal oiling system.
If you do get oil flow through the system, you might not have the distributor's "drive shaft" situated all the way down into the slot at the top of the oil pump gear?
