I am looking for information on how to go about reprogramming the speedometer on a 99' F-350 with 35" tires. At 70 mph I am really doing about 80 mph and all of my shift points are off, I have called about six different dealers and no one can give me a definite answer one said it is not possible, one said I can change the driven gear, and the others said they can reprogram it to Ford's spec's. but not for that big of a tire. Any help would be appreciated---Thanks