2.45s 8 1/4 swap..

You only need a new differential carrier (along with the new gears of course), not the axles or housing. As the ratio gets numerically smaller the OD of the pinion gear gets larger. Normally this is compensated by making the thickness of the ring gear thinner. In the case of the 2.45:1 ratio the ring gear would be too thin so they machine the diff carrier so the ring gear can be thicker. Using this carrier with higher numerical gears you do not have enough adjustment in the side bearings to get the gear mesh set-up right.

If you shop around you will be able to pick up a limited-slip differential, gears and a master install kit (bearings, shims, gaskets, seals) for under $500. If you are not prepared to install and set-up the new parts a competent shop that specializes in 4x4 work (they do a lot of axle work) should be able to do the swap in 2-3 hours.