You're going to run into a snag if you just buy the gears. The differential cases on those rears are different. 4.11 and lower use a different carrier than the taller ratios. You can buy an adapter ring to go the other way, I have one, but there's no way to use the thick ring gear on your carrier. If you want 3.08's, any wrecker will have stacks of them, they're probably the commonest (and least desired) of all the ratios available. Look close and get a posi.