I just bought a 88 Gt from a buddy of mine and the speedometer doesn't work the tach works but the speedomter doesn't he said it needs a speedo gear its got 3.73 gears in the back and he swapped over to the 140mph gauges. How hard is it to put in the speedo gear and do you think that will fix it or could it be something else? And where can I find what gear I need to get for my rear gears and tire size any help would be appreciated. 
