This guy should be on pirate, but reading not asking questions. I spent almost 2 years planning for my 4-link and it still didnt come out perfect.
Buying Deaver springs isnt much savings if you are building the 4-link your self. A rear 4-link is good on the street, but plan on chopping the f out of your XJ to get something that is worth having.
Coilovers are the best setup, but they are $$$$, almost double or more of anything else you can use. (airshocks, 1/4 elip, coils/shocks)
AKA you probably shouldnt do it now, hows that for help?