At the top of the rear roads springs there is a large foam ring that sits between the upper spring perch and the upper spring cup. The part number shown for this in the classic Jaguar parts catalog is CAC944960
It can be seen as item # 5 in this drawing from the part catalog
I searched for this CAC944960 number but it seems to be NLA. However the same part for the X300 and X308 cars is available either as MMD3565AA (OEM part number) or as SM5358 from KYB.
Anyone know if the X300 part fits a MY93 or MY94 XJ40 car?