if your asking if all GT's have a limited slip differential, the answer is yes, if you want to confirm it yourself look at the axle tag on your differential, if your car is a manual shift you'll see 3L55 8.8, the 355 is your ratio and the L for the limited slip.
Every 2003-2004 Cobra, 2005-up Mustang GT, and 2007-up GT500 has carbon fiber clutches installed in the Traction-Lok differential from the factory. Some people complained about clutch chatter, so they brought their Stangs into the dealership and got ripped off by having the dealer install the "B" clutches (regular friction material) that eliminated the chattering. The "C" clutches are the carbon-fiber clutches which are designed for more torque bias and better durability.