Dudes got a point. Just about all Exploders have the 8.8 which is stronger than your axle. You would have to set it up for your XJ so really at that point you could use any leaf pack you want with a little modification. I would guess though that it has a 3.73 gearset and a good chance it's a limited slip. You would probally have to regear the front if you wanted to use it. If you can get it for free then it's a steal and sell it for some, what sounds like, much needed cash. In fact I would say that if you can get it for free and you don't I would stop talking to you, it's that good of a deal.
Back on the leaf spring conversation. I've been researching the bastard pack for about a year. I've lost a lot of my links but I still have a few.
http://www.geocities.com/xj88driver/cherokeedodgesprings.htm Has a nice chart for the XJ's measurements.
http://www.naxja.org/forum/showthread.php?t=949841&highlight=dodge+van+springs
http://www.naxja.org/forum/showthread.php?t=66012&highlight=junkyard+finds&page=18
http://www.naxja.org/forum/showthread.php?t=66012&highlight=junkyard+finds&page=18 This one is just a good thread that has some nice pictures and has some good info for you later on in the post if this is the one I'm thinking of.
http://www.cherokeeforum.com/showthread.php?t=1380
Heres some good links for you and your getting the hang of this. Google is every wheeler on a budgets best friend. Tell you how to fix your ride without a shop, and lets you find the cheapest parts in the nation without leaving your house.
Parakeet