Need help on rear suspension

claytons does a rear coil package, do they not?
search 'rear coils' you should have some reading to do after that...

First, If I recall, both Clayton and Rockkrawler were coming up with kits. I doubt either of these bolt onto a stock tj d44, but look into those.

Second, I am not trying to be a dick, but - if you have to ask a question this vague, I highly doubt you are ready to tackle this type of custom project (if you want it to be successful). A custom built linked suspension isn't a walk in the park. Nobody can tell you over the internet how to do it step by step since every vehicle is a little different - even among XJ's... Everything affects a linked suspension from lift height to what kind of stuff (i.e. how much weight) you typically carry with you.

To truly answer your question - You need to keep searching, there is a lot of information on it. Read for hours on here and on pirate. When you are sufficiently confused about what everything means, keep searching and keep reading.

Or, of course just pony up the cash to one of the above mentioned companies who has done the math.

-JM