For 1935-1939 the heater shut off valve had a hex nut/bolt with a ball on the end that turned in to shut it off instead of the wing nut that was used 1940-up. GM part #985079. I use mine in the summer to shut off the water to the heater. They were dealer accessories and aftermarket products. They were used on both the cars and trucks. I've seen them on the water pumps, and the thermostat housing. Does anyone know exactly where they go?
