If you are SURE you have 3.73:1 gears in the front... YOU WILL NOT NEED A FRONT CARRIER to regear to 4.56:1. The reason I ask if you are sure is that 3.73 is a very uncommon axle ratio for an 1987 or newer XJ. "most" 4.0L automatic shift came with 3.55:1 (4.0L manual shift came with 3.07:1) and "most" 2.5L came with 4.10:1.
There are two carrier offsets for the Dana model 30: 3.55:1 and down, and 3.73:1 and up. This holds true for the factory open carrier or aftermarket limited slips or full carrier lockers: Two different part #s for the different offsets.
Drop in lockers (EZ, Lock Rite, NoSlip, Aussie) don't care what the ratio/offset is.
Also the rear 8.25 carrier will be OK for the 4.56:1 swap as well (but no gears available to go deeper than 4.56:1)
You could retain the factory 8.25 limited slip, but if you decide you eventually want a locker for that carrier, you only have one choice: Powertrax No Slip. The earler 8.25s had 27 splines on the axle shafts/carrier side gears but in 97 or so they were upgraded to 29 splines. 2 splines doesn't sound like much, but it is a significant increase in strength.
I wheeled a season on 33" with an open carrier 27 spline 8.25"... had no issues :dunno: but If I were going to the bother of regearing, I'd have upgraded to 29 splines (find a pair of shafts & open carrier or the whole axle assy at a junkyard and be able to use the less expensive Lock Rite locker)
