Tips for installing oil scavenge pumps?

[sactostrat]

I went through Insite's timing thread to reset the timing and, while in there, found the 4-5-6 oil scavenge pump had a cracked drive "tooth", and also noticed that both pumps were installed upside down. I bought a replacement pump but can't get it to slide in. Anyone have any tips? It seems like the tolerances are so tight that getting them lined up properly while the engine is in the car is next to impossible.