Try contacting Supersprint directly
Here:
http://www.supersprintna.com/contactus/
There web site does not mention the ML500 as you probably already know:
http://www.supersprintna.com/catalog/2004/Supersprint-Mercedes.pdf
It wasn't a perfect clean fit on my ML430 but the muffler shop was able to make some creative adjustments with the hangers to make it work and look as symetrical as possible: