Pro Comp full leaf packs.

Pro Comp leaf packs are generally regarded as giving a more harsh than needed ride. A better, and also cheaper solution would be to find a set of Dodge Dakota leaf packs in the junkyard. Cut the main eyes off of them, remove all but the factory main leaf of your XJ pack, and replace them with the Dakota leaves. This will net you a nice ride, roughly the same amount of lift, they will perform great offroad, and will not beat you to death on the street.