The screw Holley states to remove is in order to allow the A.T. "kick-down" lever to operate on the carburetor linkage shaft. Allowing this lever motion, along with a cap-screw, threaded nut & return spring are intended for attachment & operation of the "kick-down" rod linkage which is used on C4 & C6 transmission applications. On these applications a single steel tube linkage attaches from the carburetor kick-down lever down to the transmission's lever.
This is not applicable in your installation, if you retain the C.O.M. transmission & factory linkage. Scott.