Carl: Compressor has a clutch that engages and disengages as you drive. The throttle cable thing may be a headache. Don't know. The carb motors in the 80's had what you want. Guess what it is called:
Air conditioning throttle compensator. (solenoid). Example: Holley 46-74. Operates off the AC wire. $90 (ouch). Summit and etc.
Kind of a dash pot in reverse.
You are good at making brackets so it will be fun. Find a $5 donor to see if it works. Anyway, Google on it and see what you think. Lots of forum chatter.
Edelbrock has one also.
