For ZJ's, Kevin's and Clayton's are the most favored.
Rusty's make a good product, but I heard they've had issues with customer service. I never had any problems.
Another option would be Rockkrawler...They have been bashed all over the internet by a bunch of yahoo's that "heard this", and "read that on the internet", but have never run their product. They had some issuses with their 1st Gen stuff, but the new stuff kicks arse. I loved the long arm set up I had in my XJ...and the price was unbeatable. Talk to Rob from Hoyboyz...he's a good guy to deal with.
I like the fact that the Rusty's kit includes a new crossmember, but I like the fron and rear link setup on the Rockkrawler kit way better. You will get more binding with the Rusty's kit.
http://hoyboyz.com/Rockkrawler kit:Rusty's Kit: