Hi everyone. My '71 GTO came with factory a/c. When I first bought the car, some pieces were missing and since then, I've been buying parts to put it back together. A missing piece is the thermo vacuum switch that screws into the passenger side intake. I've researched this part and I see it is offered in a 5 port and 3 port variety. I do believe I would need the 5 port. Would that be correct?? I've also checked the schematics in my repair and assembly manuals, but can't seem to locate where this switch gets it's vacuum from. Would anyone know that?? Thank you very much.