The T5 transmission has a factory installed offset adaptor that screws into the transmission and the cable screws into that. If you put your cable directly into the tranny your speedo will be way-off. (high)
A company in Milwaukee "Speedo solutions" (414)
463-6660 might be able to help you get the correct gear sets to calibrate your speedo. Have your OD ratio number, and tire/wheel diameter and ring/pinion ratio available. The local Chevy dealership doesn't even have a picture of the T5 adaptor so if you didn't get one you might have to go back to a j-yard and do some looking. I have a picture of the adaptor on page 10 of my webshots "shoebox. Hope this helps.
