All I was recently swapping out the stock radio on my S320 (upgrading from cassette to CD). While I was at it, i pulled the radio in the Crossfire and found they are exactly alike in the back. I plugged the old Mercedes radio into the Crossifre harness and it worked perfectly. The only difference is that the Crossfire harness does not have the CAN bus or fiber optic connectors so there's no easy way to use the stock 6 or 10 disc CD changer.

That being said, the owner's manual for the new radio came with a pin-out diagram, which I thought I'd share with you. Hopefully it might be useful to someone that's doing a project.