Rebuilt a 79 360. Stock crank, scat rods, speed pro pistons.

Already fired up and ran for 10 minutes. Ran great. Turned her off normally, went inside and ate dinner, went out to start her back up, she started, I pushed the clutch in, she died, and now she will crank a partial turn. I can get underneath and turn it in reverse by the flywheel, and when I turn the key to crank her, she will turn a revolution, and then stop.

I pulled plugs thinking maybe a hydrolock situation, but the spark plugs are bone dry.

Swapped starters thinking maybe a bad starter, but same situation.

Before I tear my hair out, what could possibly be my issue?

Been a long week, so not gonna mess with it until morning...

Edit: oil pressure was 50psi confirmed with a mechanical gauge.