The poster on the other forum who had this modification done by the dealer is supposed to be posting pictures of what they did. I should have a better idea of the options once I see those pictures. From what others have noted, I think it's a pretty simple heater circuit that can have a shut off valve installed.

__________________
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13