I dont endorse Davis Autosports, but i browse their website from time to time to get ideas for my Jeep.
They have announced they are building off the shelf XJ's with 6.2 liter engine and transmissions and a 4 link Fox full coil over rear end. The XJ just gets better and better as a vehicle that can be modded in any way you like.
"We are very excited to announce our newest XJ build!!!!! We will be releasing the ALPHA XJ for public purchase in mid 2017. This XJ will include our full GM LS 5.3, 6.0, 6.2 engine and transmission conversion. You may be asking, why 2017?? Well, we are manufacturing our VERY own Davis AutoSports Custom 4 Link Rear Suspension System to get rid of the 100-year-old leaf springs. We are also teaming up with Fox to develop a Full Coil Over System for this set up. We have a few other secrets that we will release in due time....Stayed Tuned For More Info..."
http://davisautosports.com/
As i am rebuilding my XJ ready for engineering, i have always wished it had a stonking V8. My DD is an Overland GC with the 4.7 H.O. Might be able to get some ideas and parts from Davis in the future for a V8 swap....
Cheers,