I may be over thinking this, but I'm re-rebuilding my engine (so many mistakes) and want to reassemble the oil pump. There are dots on the impeller, are they significant in determining installation, or can I just slide them in without regards to orientation? Obviously shafted impeller goes in one way.

Oil pump impellers

 

Why aren't you installing a new oil pump ?

 

The dots are there to show which way they are supposed to mesh, both dots either up or down. That main drive impeller looks pretty scored to me. The cover plate is probably scored as well and probably the pump body cavity the same. Trash it and buy a new pump. By the time you refurbish that pump, the resulting project will not be worth all the work even if all the clearances are right. Any excess clearance between the gears and body cavity, cover plate will cause a leakage path the won't build pressure and possibly need to be primed to get any flow at all.

 

Consider the amount of money and energy you are spending on rebuilding the engine. The price of a new oil pump is insignificant in comparison. Buy a new pump!

 

Seems consensus is buy an all new pump. Thanks for the input and the information.