4spd manual? 5 spd manual? auto?
more importantly, you'll need to find out what ratio you have.
-jack up one rear tire and put the trans into neutral. then rotate the tire around exactly twice while counting the number of times the driveshaft rotates around.
-if the axle has a posi, then jack up both tires and rotate one of them just once.
if the driveshaft rotates a bit over 3 and a half times, then it's a 3.55. if it's a hair over 4, then it's a 4.10, etc.
if you've only got 3.55s, then you might want to scale back on the tire size a bit because that little 2.5 is really going to struggle. :(