I take it you don’t want ac in the car? since the ac box is vacuum controlled it would take some figuring out. If you had a non ac box to steal parts from you might make it work. Would probably be a lot easier to just use the ac controls.
How/where the vacuum servos mount on box and attach to blend doors will be a lot different from the clips on a box that manual cables attach to. I don't know if robbing parts from a heater only box to build a hybrid would work or not.
