Has no speedometer or mileage movement on his dash.

You would be able to and would have to find the connector on the wiring harness which would be hanging near or around the transmission tail. An electronic fitting near it on the tail would be a sensor for load on the engine and transmission shifting. So, you can't change them out as the wiring has to be there and if it is not hanging from the harness, it probably is just lost. It goes through the firewall into the interior rear of the gauges.

There is a speedo speed buffer that goes out on theses cars too. Here are some diagrams to help you get the problem fixed.

Here is the VSS in the transmission.

Please let us know what you find.

Cheers

It will probably help you find the speedometer cable and its route through the firewall, it has to go through the body of the cab somewhere, by removing the instrument cluster first.
I am giving you an exploded diagram of the instrument cluster, it does not show cable hookup but may come in handy. I also am giving you an exterior diagram of the transmission showing parts #30&31, in top right box, as the speed sensor and the speedometer cable drive.
The service manual I have is somewhat ambigusous as the same tranmission is in the "S" series and is cable, but the "K" series alludes to the cable running from the tranmission to posssibly a hookup outside the cab that converts the signal there and sends an electronic signal to the instruments. I am really not sure about that as the wording in the service manual we sue can be very mis-leading. I just wanted to give you the information as I could best translate it. Without supporting diagrams showing the entire path of the speedometer cable I really cannot give you a definitive answer. I think between the diagrams AI am giving you and information, it should be easy to figure out how the setup works with the truck in front of you.
Let me know if there is anything else you need.

Your very welcome.

I would appreciate the outcome as I always like to know if a customer is taken care of or not. Not only that but mechanics is a constant learning experience and I never pass up the opportunity for more information.

Take care and good luck.