priming the oil pump

I doubt you have the head gaskets on wrong. If you can find a drawing of the oiling system you’d see that the drivers side head gets its oil when the two holes in the cam line up with the hole on the bulkhead and the hole coming down from the deck on the number 2 cam bearing. When those holes are lined up you get oil.

Same with the passenger side except the oil comes up thought the number 4 cam bearing.

You just have to get the holes lined up to get oil going to the head.