From the research I have done,,, I think the XF, XJ, and other models use different isolators that would not work on the LS/S-Type. After going almost halfway through all of the Moog supplied isolators listed on Rock Auto:
http://www.rockauto.com/en/parts/moog,coil+spring+seat,10444
I have resigned myself to using the existing nylon isolators on my LS... unless Kumba gets my PM and steps into this thread to offer advice. The LS isolators were only supplied with the shocks. I have no idea why Bilstein doesn't do the same. May still try to contact Bilstein now that I have some time off. Have even thought about going to a boneyard,,, and getting one shock assembly... and pulling the isolator and sending it off to Energy Suspension.
The closest universal isolator that Energy Suspension offers is close... but not close enough to even modify to work. Also... so far the Jag site I have joined doesn't seem to be able to offer much knowledge. Possibly one poster,,,but he doesn't have eyes on his s-Type at the moment.
Either way,,, I can't wait too much longer. Left rear side is definitely hitting the bouce stop on the shock... and right rear isn't much better. My butt is sagging, (I mean the car).
BCA,
It may not be the springs that are your issue,,, but the shocks instead. From my understanding,,, that part, (MJ... whatever), is a spacer shim to adjust ride height on sagging springs. That's why it's a flat disc insted of a tapered isolator.