PM a member named Lonely Toothbrush, he has posted pics of a GS with Brabus V's in 20", and I'm almost positive that those wheels only come in one width, which is 9.5". I'll see if I can find the pic, that thing was slamdanced too!
Found it! The only thing is, the car is running a 44 offset in the front and a 40 offset in the rear, so like PHML said the 40 up front may pose a problem
Heres a quote from his post
Brabus Monoblock V's 20x9.5 with NO TIRES. In GREAT condition, just got them re-chrome so they're basically brand new. All four of them have been re-drilled to PCD 114.3mm with four custom hubcentric rings. Offsets are F:+44/R:+40. Asking $2500 plus shipping. They fit SC430, First & second gen GS300, GS400, GS430, and all LS models