My best guess is cruise control. I installed them in my cars and trucks since they first came out. Being tall, I loved them.
Anyways, they had beaded ends on them for length adjustment and some models attached right to the gas pedal. There was also some wiring to the brake pedal light switch that would disengage the cruise control when pressed. And lastly they ran on vacuum. I remember tapping into a vacuum hoses for this vacuum cylinder about 3 inches in diameter or so that did the actual pulling.
I also remember attaching a magnet to the drive shaft and mounting a little pickup sensor over the magnet.
Good Luck... Phil