Heater disconnected from the back end

When we bought this car, we noticed the heater didn't work. When we were putting in a stereo, I noticed the wires for the heater are left hanging on the back side of the dash. Great!!!!!! Even though Cali doesn't use as much heat or ac, I would still like to fix this up for the defroster to work. Has anyone ever had to rewire their heater? If so, where did you get your schematic from?

BTW - It's in a 68 Plymouth Valiant. But most darts and valiants around this time frame utilized the same type dash and components.