They will fit, but the front springs will be too soft for the heavier engine in you 550. You can look up part #'s at Eibach's website and you'll see they have one kit for 6 cyl engines and a different kit (with higher rate springs for the front) for the v8 cars.

__________________
________
2008 535i - Monaco Blue/Tan Leather, Sport, Premium, Cold (+ heated rear seats), Navi, HUD, PDC, CA, Sunshades, Fold down rear seats, CPO, Extended Maintenance