Matt,
I put a different distributor in my 261 and cranked it on the dolly. I had completely rebuilt the engine for my '59 truck.
I had just poured the new oil into the top of the engine and then cranked it. It ran a while and I observed it but after a bit it squealed and I immediately shut it down. I didn't see that it wasn't oiling from the oil poured in earlier and I had no reason to suspect "no oil supply".
I wasn't fast enough, My new bearings were toast!
The problem, though I never dreamed it could happen, was that the distributor tang didn't reach the frapping oil pump slot!
I measured, re-measured, scratched my head, measured again, made an adjustment to the vacuum advance (It can be adjusted up and down the distributor shaft) and I'm now getting oil.
Unfortunately, that lesson cost me a brand new do-over rebuild and my excitement over getting my restored truck back on the road was a disappointing set-back.
I'm not saying this is your problem, but the problem sure sounds familiar to me.
Best of luck,
Jerry
