I'm designing my own climate control system for my 1979 300D and have these extra parts for sale.
Unwired Tools ACC II upgrade kit, this replaces the problematic original controller/servo and amplifier. I sent this electronic controller to Unwired a little over a year ago for a rebuild. They installed a new circuit board that includes the vacuum switches. I only drove this car 1,300 miles since installing the controller so it is very close to new/rebuilt condition. This controller worked well with no issues. I'm including extra vacuum line and connectors so you don't have to hunt parts. I can email you the pdf installation manual for this controller $325.00 shipped in USA paypal is OK.
Nearly new auxiliary water pump I installed this new when I installed the Unwired controller so not much use, this is an aftermarket pump, it runs smooth and quiet. $35 shipped in the USA.
Vacuum controlled vent line actuator, this mounts up by the heater radiator inlet pipes to modulate the vent line flow. $35 shipped in USA.
Thermostat, selector buttons, AC switch and faceplate for ACC II cars, this worked well without issues, my car that these came from is low mileage (87,000) $75 shipped in USA.