I can answer that. Kind of. When the late great Terminal Island Raceway was open(goggle it, it was a cool dragstrip) me and my 383 '68 Dart 4sp(yea I know..I regret selling that one everyday) and my co-worker in his 69 Mach 1 428CJ automatic lined up 5 times. 5 races and I had him by 4 car lengths(his best run) everytime. Two weeks later we did the same thing but with my '70 Dart Swinger 340. 5 runs. This time it was 6 cars lengths consistently. Something about Mustangs; they just weren't fast out of the box. 340 was/is a magnificent engine. Even the 72/73s. But 68-71 were great years for that motor. Never understood why they put them in 71 and up Chargers and Roadrunners.