Stock suspension doesnt mean stock components. Not a single piece of suspension, or brakes is factory stock on those cars. FIA GT3 cars run coil overs on all 4 corners. GT3 cars are built on a tube chassis. SCCA is closer to factory stock racing where a unibody chassis is fitted with a cage. These cars have more headway. Check Youtube for some of the video's. Those cars are nasty and would annihilate a car under SCCA restrictions. FIA GT3 cars are pushing 600 HP. Where under SCCA rules the Mustang would be closer to 400. In GT3 the Mustang will be up against Aston Martins, Audi R8's, ZR1 Corvettes, Ford GT40's, Porsche etc. Its a world class line up.


Edit:

I just read the engine specs on that car. Its running a 5.3 making 560hp. I'd hardly call 5.3L a factory engine. Its also running a transaxle with an IRS rear end. Not exactly stock there either. That means the transmission is attached to the rear end of the car like the Corvettes. They would have to with the Mustang because they are so light in the ass,.. putting the transmission back there makes it easier to get a 50/50 weight bias.

Hurst