Ah - not the cables... the control rod which connects to the gas pedal pivot that pokes through the floor.
That will be harder but not impossible to find.
The reason it was removed is likely because your dash dial is broken (as usual, and I can rebuild it) and was set to a speed that is low enough that the gas pedal gets the pressure feedback (as designed) when the car is going to exceed the preset speed. Annoying, so often the rods were disconnected and removed, and then lost over time.
Check to see if your dash dial will adjust - if the dial seems to smoothly engage and the numbers go up or down, then it's likely OK. If not, the plastic gears within are toast.
If the dial seems to work, then it's possible the servo needs some love.
I will check the rod's part numbers and see what cars they're used on - you might still be in luck if they cross over to Imperial, as more Imps were equipped with Autopilot than C bodies at that time.
Update - you're in luck - the rod is the same. It has an important little guide bracket that goes with it to permit adjustment for length, but the same rod and pivot are used in C body and Imperial.
ROD - AUTOPILOT LEVER TO AUTOPILOT - 2843 790
I might have one if
@detmatt doesn't.