My understanding is 37 "will" fit on a 2.5, but have approx 2 Inchez of up travel especially if you go with a negative offset. 3.5 will work with a smaller 37 like a KO2, but for full off-road capability you really need to change the fender to flat/high line and maybe look at 3.5 to 4 .5 inch lift. But I would wait to hear from someone much more knowledgeable than me, like Matt.