Holley's either have the kickdown or not. It's a lever inboard of the throttle lever with an adjustment screw and return spring. It's not something that's necessary, you can always down shift manually using the shifter lever. There would have also been a hollow steel tube extending from the transmission up to the carb, that would be the kickdown rod. If your car had a 2 bbl carb origianally and is now a 4 bbl, the original kickdown rod would have been too short to work anyway.
