I might tend to look for one that changes the frame side bolt to a "front to back" combination as opposed to a "top to bottom". This will allow for more flex.
Frame side trac bar mount from ballistic. Definitely not "made for XJ", but you aint going to beat that price and setting up the rest of it is doable for an easy price.http://www.ballisticfabrication.com/Pan ... _1441.html
Take that measurement of 4 inches from the bottom of the frame to the center of the bolt hole, and go see what your factory one is to the middle of where the bolt is that goes through.
Interesting idea here. Doesn't look like they make it any more, but making your own cross brace would not be hard. The way this guy did it is cool, IMO, because it is adjustable.
I don't like the pure bushings as that would be a big wear point, but I am sure it "rides" softer like that...