Dr Time, the only thing you would hafta swap doing a gear swap would be the third members. You can either have a new ring and pinion installed onto yours (and whatever shims seals and other bearings are needed) or just swap out your third member for another one. For the rear all you gotta do is drain the gear oil, remove the brake drum, unbolt the four bolts on the back side of the backing plate and slide the axle out. Sometimes the axle comes out easy, sometimes not. Repeat for the other side, unbolt your drive shaft, then remove the bolts holding the third member and pull it out. These are just general instructions however.