If your car is stock, you're out of your mind, if you want to talk modded vs. modded, you're out of your mind.
I'm loyal to the death to classic Mopars but even the regular GTs are a $7k bolt-on blower away from 10s. Guys had these cars in the 8s within two months of the Coyote hitting the streets.
Sorry but as great as the classics still are, you just can't beat the march of technology. Modern cars have built upon everything good from the muscle era and added 40 years of refinement. The only disadvantage is the weight of all of the safety crap, most of which can be earily removed if you want to get serious.
That said, if I had to let go of my Dart or my Mustang, the Mustang would go bye bye first.