I would like to know how to re-calibrate my speedometer in my 58 Impala. The transmission is now a Turbo 350 and the speedo is reading about 15 mph too fast. I know there is a small plastic gear on the tailshaft that drives the cable and a gear inside the tailshaft that drives the small gear. Do I need to change both gears or just the small driven gear? How can I tell how many teeth I would need?I have a 3.36 rear end and 2.25X78X14" tires. Thanks
