The changeover from Autotemp II to a heater only system uses the control switch system and cable from a B-body such as 75-79. The cable operates a pull-to-open water valve in the engine room. The B-body control switch is one from an a/c equipped car. I used the NYB original a/c, heat box and heater core. I removed almost all of the autotemp operating system (dash switch controls, most of the vacuum lines, servo motor, autotemp specific wiring). I secured the servo rod (which operated a door blending cooled air with heated air) in the full heat position so all air flow goes through the heater core. The cable operated water valve then controls the temperature. Most of the plastic vacuum lines get reused. Use rubber vacuum hose to connect the B-body vacuum switch to the plastic lines feeding the appropriate vacuum motors. A factory service manual is quite helpful with this. The blower motor I wired through relays (one relay for each blower speed) using the original resister block for the different speeds. (The resister block from a B-body is a little nicer to use for this.)