The cruise control in a 68 Caddy I had was different then how they
work today. It allowed you to do the normal cruise thing at a set
speed and the car would take over the throttle. Or you could set the
speed in it but not have it run the throttle but run it yourself. The
difference was that with the second way the servo tracked the throttle
position and speed and if you tried to give the car more gas then was
needed for the set speed it started to push back against you, you
could easily feel that it suddenly became harder to push on the gas
pedal. The faster you went over the set speed the harder it pushed
back. It used all rods and levers, no cables. It was great for heavy
traffic where you didn't want the car to control it's own speed but
still wanted to make sure you didn't go over some particular speed.