Back in the 70s I installed a fresh 440 in a 68 GTX, and had the same problem.
A chevy shop had hot tanked the motor and not replaced the plugs..

The customer drove the car for a week before we found the problem..No oil gauge..(back when there was one car and you drove it or didnt get to work).

No long term problems with that engine..Ran High 12s the next summer..