You first need to find out what overdrive ratio your T5 has and then pick a rear gear to match. T5's range in OD ratios from 0.18 to 0.33 (or 0.82 to 0.67). A non world class T5 is a very weak transmission so if that is what you have I'd forget tire smokin. World class ones are stronger but still a wimp transmission as far as tolerating high torque. It is much easier to find w/c ones from Mustangs and they usually have the 33% OD. If you have a 4.57 rear and a 33% OD T5 then your final gearing with in overdrive would be 3.06 which is a very good road gear. An 18% OD T5 would give a 3.75 final---not so good.
