Just wondering about the aluminum parts for the new Mustang GT's, does the aluminum flywheel and driveshaft hold up as well as the stock ones? Are they just as strong, stonger, weaker?

How much would they actually help out as far as rear wheel horsepower?

 

hp difference will be only coincidental.

the reduced rotating mass of both items makes your engine work less hard to achieve any particular RPM so it spins up faster and slows down faster. They hold up just as well if not better in some cases than the stock pieces.

If you are a dyno racer and only care about numbers on paper, those will do nothing for you. If you actually race you'll appreciate the actual benefits quite a lot. There's not a bit of seat of the pants change unless you're really in tune with your car.