I am not sure of the make/year/model, but when I built my 440 for my 71 Road Runner, I used a Holley carb that had a fast idle solenoid mounted on the throttle arm shaft. When the ignition was switched on, it pressed on the throttle arm and opened it slightly. When the ignition was turned off, the solenoid would retract slightly and prevent run on. Also, I used an MSD ignition, which helped a lot with driveability and smoothness and holding the 'tune'. Good luck.