See the phone bulletins (no, that's not a mistake) for the model years you are interested in, at Phone Bulletins. Installation diagrams and part numbers for the changer are in the bulletins.
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2005 S500 4-Matic
with Gateway 500 iPod integration
Formerly: 2000 S500
with Ice>Link iPod integration
Moto V710 phone with MikBox
Upgraded Voice Control