If (hopefully) your T5 has the original aluminum tag with the trans number, you need to check the number on several sites to see what the gear ratios are. If it has the .86 5th gear and 4.03 1st gear, you Might, be OK with the 3.55s. It's going to depend on tire diameter, terrain, and how use your truck. I'd install the T5 and see how it works out. If overall gearing is higher than you like, you can always shift down to 4th.
Good Luck,
RonR
