I've been looking at the photos. I think you are on to something. You should be able to buy the 3 hose assembly and just add two Y connectors to adapt it to the front dash use. That is assuming that the connectors are the same.

I'll compare what I have in the front of my car to the photos off of http://v12uberalles.com/Rear_AC_System.htm.

The photos in the first entry of this page sure look like they have the same electrical connections.

-Jim

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1995 S350D, Green with black leather interior.
Bought January 2008 w/ 233,xxx miles.
I did 22,000 miles during the first year of ownership.