Pretty much anything that is Chrysler specific, since the car was only produced for 2004-2008.

That would be all of the exterior and the interior from the bulkhead back. Other notable differences between the Crossfire and the R170 Mercedes (SLK 320 from 1996 - 2004) is the engine cover/airbox is specific to the Crossfire, but quite a few Mercedes boxes will fit, the exhaust system is a single center exit and wheels are staggered in width and height front and rear. The bulkhead cover on coupes is impossible to find for example, all will eventually crack. I intend on putting a nice custom diamond stitch cover over my crack one

But pretty much anything mechanical, electrical, suspension, etc. can be found easily with Mercedes parts or their numerous OEM suppliers.