Since it's mounted off to the left, did that cable run to under the hood, rather than the throttle pedal?
Looks like that was a higher trimmed truck. That passenger door panel is the Cheyenne type.
the passenger door didnt match the driver door , heres a pic of the dump truck
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You can see the door panels are different so prob a donor door on one side
This c65 has a lot of gears plus what I think is an auxiliary overdrive or gear splitter, that switch maybe for the rear axle taped to the shifter