We have worked on the BMW E39 M5 back in 2001. We put on Bilsteins PSS 9 coilovers back then and the Remus catback on this M5 rego:S10NG if anyone remembers the car.

We also took out the V8 Dyno trophy with that car at the Perth Auto Salon in the same year.

Anyway, the E39 M5 and the E39 540 V8 shares the same suspension.
Will PM you info and pricing tmr and make sure they are for the V8 versions.

Regards.