I did the same swap, but I used a long shackle of unknown origin, length of it was 8 3/4" eye to eye. Remember that MJ spring perch location is 1.5 inches narrower then that of a XJ. I am still using my front mounts for my shocks at this time, but I am fabbing up my own crossmember to go behind the axle. I plan on using XJ rear sway bar mounts( the ones on the axle) as a form of a bar pin eliminator, so I can have some adjustability on shock positioning. My problem when I did my SOA swap was the amount of rear drop I had. I ended up having to make my own set up for my brake lines. I took a standard 22" SS braided line, and a 12" steel line, I had to buy a union, and make a mount extension, but now I have planty of flex in my lines. I got my shock mounts, and spring perches at Advance right out of their Mr. Gaskets catalog.
Patrick