4.5"
to match your current rear axle you'll need the right width, bolt pattern, and ratio. without using spacers to change the pattern or paying for regearing you're more or less limited to the:
MJ/XJ 44 (rare and mostly 3.07, 3.55)
TJ Rubicon 44 (rare and expensive and only came in 4.10 but had an e-locker)
97+ XJ 8.25 (3.07, 3.55, some 4.10)
03-07 KJ 8.25 (3.55, 3.73, 4.10 and disks)
96-01 Explorer 8.8 (3.55, 3.73, 4.10 and disks)
did I miss anything?
I prefer the 03-07 Liberty because it's a couple inches wider than the stock MJ axle (as opposed to the 8.8 which is narrower) and that works well with the MJ's wide butt (the bed is wider than an XJ body which is why the tires looked so tucked-in back there). you'll still need perches welded on and to shorten the driveshaft, but that's the case with any upgrade axle. dana 35s have a bit of a short snout.