Your 93 would be an AX15, the 87 would be an AX15 if it has a 4.0L.
Output shaft casing I'm guessing is the Adapter Extension Housing. Could that crack be welded? If it can be welded, can it be done while it is in the vehicle?
Freeze!
The 1993 will have the "internal" AX-15 (the slave cylinder and throwout bearing are combined into a single unit.) The 1987, however, will have the Peugeot BA-10/5 (barely fit for scrap metal,) and it has no parts in common with the AX-15 (they're not even made by the same company.) They share clutch friction, and that's about it. The BA-10/5 may be readily identifed visually - the case is split longwise, with a parting line visible on the bottom. The AX-15 is split into three sections - forward, middle, and rear (with lateral parting lines.)
If you've cracked the transfer case adapter housing (in between the rear section of the transmission case and the transfer case,) you can replace just that - you will need to source a replacement, of course. The XJ used the AX-15 from mid-1989 to 1999, and all of the transfer case adapter housings should be the same. Check under 238ci V6-equipped Dakota pickups as well, since the AX-15 was used in there (I am not sure if the transfer case was "clocked" the same as under the XJ, so pay attention there.) Don't get the housing from a YJ or a TJ, as the transfer case is definitely "clocked" to tuck it farther up into the belly, and you
will have to modify the transmission tunnel to fit the transfer case.
"Output shaft housing" is the generic name for that part - if it's on a 4WD transmission, it's the "transfer case adapter housing," and on 2WD it's simply the "tailshaft housing" or "tailcone." The difference? Provision for mounting a transfer case.
Yes, you can have aluminum parts welded, but it would cost a bit more than typical welding. You'll need someone who can TIG weld (I believe aluminum can be MIGged, but don't hold me to it) and TIG rigs aren't necessarily cheap. Where's it cracked? You can save some money on the weld by prepping it yourself - you would drill about 1/16" right at both ends of the crack (it's called "stop-drilling," and it's a standard practise in crack repair,) and use a grinder and a carbide burr to gouge the crack in the surface for fill with weld metal.
Considering that the housing would need to be degreased thoroughly so you don't have "blow-outs" in the weld, you may as well remove it.
NB: If you get stuck trying to describe something, recall the old maxim - "A picture is worth a thousand words." It can help considerably if you show us what you're seeing!