Your problem is that you have a rusted crank, cam, lifters, and bores. You might have prevented it by using something to turn the oil pump drive shaft to push the water out of the bearings but it might not have made any difference. What you need to do is begin with a complete tear down inspection. Use micrometers and feeler gauges to check clearances and look closely at bearings and the journals they ride in.
At the very least you need to remove the heads and pan to visually inspect the bores and bearings. If there is any rust on the crank or rod journals then you need to finish tearing it completely down.

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Paul
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retired mechanic after 35 years
specialized in Holley carbs and Ford Automatic Transmissions