Oil pump 5 hole versus oe 6 hole pump for slant 6

Take apart the old pump and see if it still binds. Might just be crap inside of it. In my experience a high percentage of used pumps are still within specs.

The 5 vs 6 hole thing is a non-issue. Pumps swap back and forth with no problem - there is a small subset of 5-hole pumps that are not cast with the extra ear that blocks where the 6th bolt goes into the block. For these few pumps, just stick a little extra gasket material on that area, it will be clear when you have the part in your hand.