Have you looked into the frankenlift by Allj's?
http://www.boulderbars.com/kjproducts.htm. This lift seems to be one of (if Not) the best lift for the kj. All of your choices seem very good. the opnes i would recommened are the rustys and the frankenlift. The rockfatherII is probbaly a good lift but for the price you can get a frankenlift plus some extras!! Rustys also has a good lift,i know that some have had troble with he rear shocks that come with this lift, but if you ask iam sure they will swicth them out for some old amn emu (OME) or ranchos. Ensure that you inform them that you are going to install a ARB bumper and will need some coils to accomadate the extra weight. The ride might be a bit rough until the arb is installed but i have heard that others actually like the feel of the siffer coils.