440 Oil Pump Won't Prime

You dont need vasoline to prime a gear (PD) pump. They will pump air as long as the gears are wet with a light coat of oil. I see you solved your issue but for future readers you could have tried removing the oil pump and filling the inlet side with oil from a squirt can. Wouldnt work on a small block but could be a good trick to expedite priming on big blocks and slants.
The only problem with a slant is, you cannot turn the pump independent of the camshaft. You can prime them, but it's a little more in depth.