I recently got my AC system running after 40 years of not working on my '72 C20 and immediately encountered idle issues when the compressor was on. Found I needed an idle stop solenoid (found on Rock Auto) but was missing the bracket that bolts to my Q-jet carb.
I found several threads discussing the solenoid and even the bracket but none ever had a part number for it, only members selling NOS ones. I found that the bracket for a '71-74 Corvette will fit the Q-jet and solenoid and
they sell it at CorvetteCentral.