Check what parts you are getting as the V8 exhaust on the 430 is pretty much one piece down to the cats .... the CLK 55 exhaust is two pieces after the cats IIRC.
If he's just giving you the backbox , you will need to get the pipe cut and welded on ...
If however you are getting the whole thing to the cats , or are modding it to fit a 320 or 230 ..... game on !