You're looking for Ground Control coilovers. They're really expensive, but if you spent $$$$ on 18" wheels for a 528e, it probably doesn't make much difference to you ; -)
With the ground controls, you can select your own spring rates and shocks, and you can adjust the right height, as well as corner weights. It's really a trick setup. If I had the cash, I'd go with it on my '87, but I'm happy with the Bav Auto / Bilstein Sport setup right now.
Hope this helps.
Brad "Shifty" Couvillon
'87 528e <--- Mark D'Sylva chip, 3.46 diff, 5-speed conversion, Bav Auto / Bilstein Sport