You can swap the carrier out and keep the stock ring and pinion set. That is how I started out and then when to the taller gear set. You will love the traction with the posi/LSD. What you do is remove the carrier and ring gear, unbolt the ring gear(LH threads), put the ring gear on the new LSD unit and bolt it to the carrier with locktite applied, set it in the housing and get a rough backlash setting with shims (slip fit) and when you have the proper backlash you add .004" more shim to both sides for case preload. After all that you just put the cover back on with a new gasket and add the fluid and additives if your LSD specifies it. My Auburn says no to synthetics and comes with an additive you have to put in the case when filling it.