challenger a/c heater question

on a 72 challenger a/c car,the vacuum line that goes to the engine to control the vents.Where does the line enter the car at from the engine???

Not 100 percent sure but I thought it was just under or behind the heaterbox passenger side.

cool,i think i got it.I figure i better be on the safe side and hook up the defroster since its cooling down and going to go to a few shows in the next couple weeks...