what speedo gear do I need?

To be honest the speedo gear you have now should be the correct one.

Putting a 140MPH speedo in shouldn't affect calibration at all since the speedo is already calibrated.

Only thing i can think of is that your '83 T-5 is one of the early non-WC t-5's that uses a black 6-tooth drive gear instead of a 7-tooth.

You'll have to pull the speedo cable out and take a peek with a flashlight at your drive gear.

If it's black it's a 6-tooth
If it's yellow it's a 7-tooth
If it's green it's an 8-tooth

Then you can look on this page to see what you'll need

http://www.steeda.com/products/speedometer_recalibration_gears.php

Well, i've found out your t-5 is NON-WC. 1983 and 1984 were non-WC. Early 1985's were also non-WC as the World Class t-5 was an 85.5 debut.


That makes me think you have a 6-tooth speedo gear and not a 7-tooth....which makes sense since the speedo is now slower