green wire to heater motor (under hood)

I have a green wire sticking out of the blower motor under the hood and don't know where to hook it up, it's a 74 duster that had a 6 cyl with air now it has a 360 with no air,I have a new wiring harness from year one and it doesn't have any green wire from the bulked to hook into the wire on the blower motor, where do I hook the green wire to?
Thanks