[Aarongriffey]

I’ve had that happen a few times.
Take out the spark plugs, add six more quarts of oil to the crankcase, remove the sending unit, pour oil down the galley where the sending unit came out of, crank it over with the starter until oil comes out where the sending unit goes, drain the excess oil out.
I now make sure the oil pump is primed well before installing it.
Fill the ports on the top of the pump with oil and turn the pump drive by hand to see it actually pump oil out the top.