Could you not make use of self contained self levelling Boge shockers from Volvo 700/900 series estates, i don’t know if the V70 range of estates continued with this type of self leveller.
Quite likely other large estates had similar independent self levellers, Subaru Outback might be one that rings a bell.
Arguably if seeking used parts (yes i know new Boge self levellers cost a kings ransom) Volvo units are likely to be knackered due to the mileages most cover.
That system of Dan’s sounds the dogs danglers, you’re wasted on bloody lorries Dan you should be designing patenting and manufacturing things.