1989 XJ40 rear shock absorber assembly

Greetings fellow Jaguarist and a Happy New Year to one and all …

Lately I’d noticed that the left side of my car is about 1/2" lower (measured at the rear wheel well) than the right. Pulled the wheel and the spring looked normal. So thinking that the only things that determines the ride height are the springs I decided to rebuild my assemblies. I purchased new rear springs and all the bushings to do the job. I’ve also ordered a set of Bilstein shocks which I haven’t yet recieved.

My question is that although I’ve rebuilt these assemblies several times in the past I don’t remember
using parts 4 and 6 in the illustration below. Did the shocks I used in the past have this welded on?
I hate to pull off the assemblies and then find out I need to order and wait for those parts.

Screen Shot 2020-01-14 at 11.35.06 AM

Dont know Jags (yet), but do know Porsche with Bilsteins. The springs used with Bilstein gas units are different from those used on non-gas shocks - Porsche WSM advise going from non-gas to gas shocks can lift ride height 10mm . Do the Bilsteins ordered come with adjustable lower perches ? Item 4 looks like a removable perch (bottom spring platform), which in non-adjustable setups can be welded on the shock body. Unclear what item 6 is to me. Depending on the springs you may find the ride much firmer, some say harsh. Hopefully you are doing all 4 corners?

The KYB dampers have the lower spring seats as part of the repair ‘kit’.

The OEM spring seats have the split collets(6) and spring seat(6).

The plastic ‘shims’(2) have an affect on ride height.