A bogged down drill is a good sign. And you have fresh
oil in the heads. I think your gauge or gauge pressure source might be to blame.
With the removal and install of the distributor did you adjust the timing?
I had the same
oil priming problem in a 4-cyl: purchased a built engine, installed it and had no
oil pressure, tried everything to get it primed, when I dropped the pan I found a flat piece of thin plywood in the pan. It was getting suck onto the oil pick-up, and no oil was getting thru. the pain was troubleshooting it (as I'm sure you now know
).
I still can't figure out how the wood sank.
I happy to hear you have oil up top (read: you can now take one step back from the edge of the cliff).