The factory A/C cars had them stock, can't use the A/C and get cold air otherwise. The late 72-74 valves can be purchased at Kragen (or O'reilly's depending on your geographic location). They work for the 70-early 72 cars just fine, but they don't look stock for those years. They typically have a cable that goes to the heater control panel on the A/C cars, but can be operated manually just fine. I don't have a cable for mine at the moment so its zip-tied closed so I don't bake in the summer. No, my A/C doesn't work.
Bypassing the system is fine too, but only if you never want to run your heater. I drive mine in the winter, so I need the heater to work about half the year.
