yours is a '96 GT, I have a '97 Cobra with a similar problem. I think the other fellow is refering to a newer rig. The '99 and up's are adjusted elecronically. Mine had the gears changed to 4:10's, then to 3:31's. The speedo gear at the trany tailshaft would normally be the way to change the calibration. For my cobra 19 tooth (pink) is stock. I went to change it (very easy job), but the driven gear was already 19 tooth. Anyone have any thoughts on making my speedo right. It's off about 20%(slow).