I have the Radio out of my 56 to change the Wiper Motor to Electric. I have a Vacuum Line coming from each side of the Dash which are for the Heater with the  Vaccum Valve on the Engine. There is a "T" in the middle where 3 Lines connect together. Where does the Line comming off the bottom of the "T" connect to? The Line from the Passenger Side is connected to the Vacuum Valve on Engine I assume. Where does the Line on the Driver Side connect to? Can't tell as it disappears on top of the Heater Box. I wonder if that "T" Line is to go to Windshield Wiper Motor? It was disconnected under the Dash when I got the Motor out.