On a sct u set rear gear ratio and tire rev per mile based on tire height. The gear is for changing gear and revper mile is for changing tire/rim size.
When I made my purchase from American Muscle, I was asked all the info on car. I thought the speedo cal. was taken care of. Now after talking to SCT and plugging into the car I have discovered a whole new world of info. All I needed to do was select new rear end ratio and bingo, all is good. I have a totally different car with this mod. I would show you pics but I can't get them to download. Besides a K/M cai, Eibach lowering, Axile back exhaust the 4.10 from 3.05 is the sh-t