360 vs 383

A friend of mine ran a 383, 4 speed 68 or 69 Road Runner that he bought new, It would occasionally dip into the 12's. He had the heads milled, the stock AVS rejetted, and added headers. He tuned and refined that car for years. Not sure what gears he ran, but I'm sure they were steep. He used roller hubs to flat tow it to the track.
I also knew a guy that ran a 68 Dart 340, 4 speed that took it to the track and dipped into the 12's. He was "informed" it could not be stock to run those times. He never bothered to go back, since he bought it new and knew there were no modifications.