I worked on the 1st 38 767 at the Boeing Everett plant (1981-1983). You are correct. The 1st 767 had a 3 a Flt Engr. At that time, there was a floor panel behind the Flt Engr. He could pop open the latches and 3 telescoping levers were there to Alternate Extend. But with the design change to 2 man Flt Deck, they removed the levers and installed a DC motor to drive all 3 cables.
For alternate gear extension, the guarded alternate extension switch on the P3-1 panel energizes the electric actuator to the extend or retract position. In the extend mode, power from the 28 VDC Hot Battery Bus passes to the actuator when the alternate gear extension switch is positioned to extend and when the landing gear lever is not in the UP position. When the actuator has reached the full extend position, the extend limit switch will open breaking power to the actuator.