I found a rear supension kit but it says XJ6? Is this the same as a 1989 XJ40 kit? Every time I look for XJ40 parts ot comes up with CJ6! The part I found is # jlm11698k from welsh enterprises in Ohio, any experienced, or not addvice would be helpful. If you saw my previous post I need alot and figure at this price I will replace everthing.
Looks to be the correct parts, with a reasonable set of coil compressors you should be able to R & R each side in an afternoon. I wold be concerned that the top hat has been damaged by the lack of the isolators.
I managed to do a shock change in an hour on one side, from jack up to jack out. It takes a bit of finagalling to get the shock/spring unit out with the standard unit and have had no experience with the SLS so that might mean a greater degree of dis-assembly is required.
I just wish someone had told me how easy they are to remove when I was replacing the fuel pump! 5 bolts and there is the pump!
David,
I have a copy of the official Jaguar ‘non-Sportspack’ ride-levelling system deletion package for an XJ40.
‘XJ6’ or ‘Sovereign’ or ‘Van den Plas’ are simply trim level designations for XJ40 cars produced by Jaguar with VINs ranging from 500515 to 708757 between 1987 and 1994 so if your car has a VIN in that range it is an XJ40 whatever model designation it may have.
The official Jaguar conversion kit for your car comprises items 1,2,3,4,5,6,7,8 on the illustration below plus the damper assembly which should comprise items 9 thru 17 in that illustration.
You will read in the XJ40 and Modern list archives of problems some have experienced with ‘cheepo’ conversion KYB kits and others which failed to include the longer standard road springs.
Others have not replaced the top mounting plate (item 7) but the ride-levelling version of that is slightly different and it is important that you use the guide bush CBC2933 (item 14) which needs to be properly located in that top mounting plate.
Pay heed to the advice from ‘Grooveman’ and do a ‘proper job’! 
True for the early ones, later models went in-tank, totally different animal:)