stupid question about gearbox bolts

I recall having to fight one of the gearbox bolts all the way out in my 69 Dart long ago (though internal nut wasn't spinning like yours). Comparing to the others, I finally realized it was larger (1/2" instead of 7/16"). I guessed a guy at the factory got the wrong size bolt and just turned up the impact wrench to make it work. They didn't stop the assembly line in 1969.