My 53' Merc (which should be similar). The vacuum line goes from the bottom of the fuel pump (dual action used on the later cars) through the firewall to the "T" under the dash. One side of the "T" goes to the top port on the wiper motor and the other goes to one of the ports on the wiper switch. The bottom port on the motor is left open. The motor is turned on with a cable to the plastic slider piece (shown with a arrow). The switch has two vacuum lines on it along with a cable. The cable is used to control the plastic slider (on and off switch) on the motor. The two vacuum lines (one goes to the vacuum feed of the "T") and the other goes to the top of the washer bottler washer, with the other line from the top of the washer bottle going to the washer jets on the window.
The 2nd to the last picture shows how to hook up the system.