The Crossfire is definitely not the end of sharing MB parts; As juddz stated, the 300C is built on a C or E (I always mix them up) chassis, which is also what the Magnum and Charger are built on.

There is at least one ME Four-Twelve floating around in DCX's possession. They had it at SEMA last year and it was also featured in an Usher Movie/Video at the beginning of this year among other things I'm sure (it's a fully operational)...