Keep in mind that prior to 1972, engine HP was rated by the "gross" method, with no exhaust restriction, belt driven power accessaries, etc, starting in 72, the "net" HP ratings came into effect, the numbers were considerably reduced. Add the fact that it was also around this same time that more stringent emission regulations were coming into effect, played a role in some very low HP ratings. Example, both the 289 4 barrel engines from 1966 and the EFI 5.0L engine from a 87-93 Mustang were rated at 225HP, but in real life, the 5.0 is much stronger. As much as I love the "old tech" engines, and I would be pulling for the blown 312, comparing stock vs stock, I can`t imagine that 300 HP rated Cobra engine would having any problem running away from a 300 HP rated 312. Sure, like any engine, a well tweaked 312 can run much stronger than how the car left the factory, but then, so could the Mod motor. Factor in the 3 speed manual, or FordOMatic the 57s had, thats a further handicap. That said, I am still somewhat a "dinasaur", my 59 2 door sedan is getting a nearly 50 year old 428 Cobra Jet and 4 speed Toploader, because I still love the old stuff, and if some guy in his LS swapped 57 Chevy, Coyote swapped 57 Ford, or Buick Grand National leaves me in the dust, so be it.