Not sure of the question but…
A rear axle from a late model Explorer is best with Disc Brakes.
The cost around MA/NH Area are going for $150 and up if all the parts are there and depending on the milage.
The Ex Axle will need to be mod’d to fit, search out on the site, there are write-ups on the mod.
The Ex Axle is a little wider, approx 2” than the Ranger, me I don’t like that but other have no problem with it. If you don’t go Ex Rear Axle then the only option is a Lvl II Axle.
Gear changes, re-gearing the rear is the easiest part, re-gear before pitting it in and the front diff will need to be re-geared also. (You didn’t fill in your profile so I do not have any idea if you drive a 2x or a 4x).
If you re-gear the rear you need to re-gear the front with the same ratio or as close as possible.
Re-gearing is based on tire size and rpm nothing else. Tire Size/RPM = Power or at least the feeling of power. (Fake Equation)
Re-gearing cost for a 4x would run around $1000 maybe $1200 if all goes well.
I hope that is what you asked for, if not sorry and just ignore what I said.
4x4, 5sp, Std Cab, Stepside, E4 Red
4” Lift - Coil-Overs, 6” SkyJacker Leafs - No Blocks (Mistake)
31 Spline FX4 Rear Axle, 4.56s and OX Locker, Hurst Shifter w/Optional Stick and "Made by Grev" alignment adapter