Even with the GT500 rear valance, you'd likely have to adjust the hangars on the kit for a proper alignment. Not to mention, the 2013-2014 GT500 Valance still requires you to cut your Mustang's factory bumper for installation. Either way, there's some slicing and dicing of your car involved. You can call us directly at 1-877-578-2433 for more detailed information, if you're still dead-set on this setup.