The bmw backbox wont fit without some serious mods to the car, the main one being you'll need to cut out the spare wheel well. Powerflow will be able to custom make you one that looks the same, but I think you'll just have to cut up a standard valance to fit the tailpipes. Or you could always go the R32 look, you'd need to buy the complete bumper for that though, and then you'd have to get a matching front bumper/sideskirts or it'll look odd.

Again, you'll have to go to someone like Powerflow to custom make you the exhaust. Hope that helps !