I'm almost positive the GT's came with 3.27's also. And the 8.8 will bolt right up, with no problems. Your best bet is to find a 8.8 with 3.73's or whatever with them already to save from some of the hassle of installing them, but your 7.5 rear is pretty strong too. You just need to take care of it by doing annual fluid changes and the such. Your basic maintenance.