water valve in the heater hoses

Where they factory or just aftermarket deal. My 81 Dodge truck has one, but it's vacuum operated. I was at the dealer ship getting some Mopar heater hoses(cause I it's cool to have hoses that say Mopar on them). They were were tripping cause I don't have one on my car. I was looking a my 64 to 74 Cuda book and couldn't see any of those cars that had one. Can some one explain the deal on that, if doesn't have one the how does the heater box in the car keep from getting the inside of the car hot in the summer time from the water? Thanks for your time.

Lee