T5 Speedo Gear

if the speedo was accurate with the old settup, you can use the same gear and speedo cable with no problem. it should just plug in. but in order to give you the correct driven gear, i would need the rear gear ratio. you can test the speedo to see how far it might be off by driving the car ten miles(a know distance of ten miles. best to use the mile markers on the road). if the speedo is accurate, it should read 10+- 2/10 miles. that is about as close as you will get. if your odometer reads more than the 2/10 mile error, then you need to change the driven gear depending on how far off the odo is, and which way.

I used this site to figure out which speedo gear I needed:

http://www.hanlonmotorsports.com/t5speedo.asp

You will need to know your rear gear ratio, but maybe you can figure that out based on the stock speedo gear color that you have? Google search? Hope it helps.