The P15 Plymouth 1946-48 were often used as taxi cabs. When used as a taxi a double action fule pump was comonly used. How was the vacuum partion on the pump conected to the wiper motor. There are two threaded ports on the vacuum part of the pump . One port to the front of the car one to the rear . What should be connected to each port.Any information referance or photo of a double action pump instaled on an L-head engine would be helpful .