I did ox lockers front and rear as well as a full float rear kit and chrome moly’s in front. You can get everything from on the Rox. I had a shop do the install. If you’ve never done gears before or don’t have the proper tools you can easily botch the install and have to do it again with new parts. It took them about a week mainly due to running into problems getting the rear axle out. They had to make a tool. No idea what it did to my fuel mileage, I don’t track it. But it did make my crawl speed much slower which works out really great driving around the house and out in the pasture.
I went 4.56, CM axles all around, Detroit TruTracs and 33” tires.
With the tire swap I maintained the original rpm/mph. Fuel mileage appears nearly the same as stock, down a very small amount.