Did a quick check on Parts.com and attached the 2 engine parts diagrams for the 2003 ML350 v 2003 SLK32 for ref.

I checked prices against each other but that wasnt very conclusive.
The inlet and exhaust valves were identically matched (in price at least).

It would be good to have a similar search engine that reported back part numbers (MBenze or Mopar)
But I dont know of such an animal - links appreciated.
Of course if they have the same PN, that's a good thing, if they have different PN's then I guess you gotta dig a bit deeper to determine if they really are different.

later I found the second image for the SLK320 v SLK32 but it doesnt have cam/crank detail