I know my username is old, I just purchased a 2003 Mustang GT and I would like to put a t-lock upgrade in the rear end. I'm assuming the GT's have the 8.8 rear end correct? Also how can you tell if you have the 28 spline or 31 spline without tearing it apart? I was at americanmuscle.com looking at them and I don't know which one I have. Thanks for the help.