I know this is smaller than you're asking about, but I run the new Rubi wheels on my xj.
Size is 285/70/17, Kevlar. Synergy hub centric spacers.
New Years Adventures by
Sean Mitchell, on Flickr
I thought those were all 18". They are really nice looking wheels. Here in N.E. Florida a bought 5 of the plain 5 spoke 17", 4 tires with 80% or more thread remaining and the spear that have never been used for $200.00. Those wheels on your XJ are offered for $800.00 and up for four. I would have loved to get a set of those but the old pocket book was/is a bit too flat.
Those are Rubicon wheels? Are they 5 X 4.5 bolt spacing? Those that I have are 5 X 5 and need an adaptor/spacer. I will be getting 2" spacer to give an extra 1" width on each side.