Might want to pull the distributor out and try to turn the oil pump with a screwdriver.
A couple months ago we pulled the distributor out of what we thought was a good engine, but the tang was twisted off the distributor, apparently the oil pump was frozen and when the engine was turned over the distributor turned but not the oil pump, twisting the tang off..

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-