You'd have way more work converting over than you'd think...You're better off just buying an aftermarket heater control valve and just let the a/c stuff there...There's a bunch of aftermarket valves that are much cheaper than the NOS bakelite units out there...They don't look the same but work just fine...
So all you really need for heat would be the valve,check the cable from the dash switch to that valve for smooth operation.. Then check that you have a non-leaking vacuum system to operate the plenum doors...