1970 Dodge Dart Dash Removal

Many factory service manuals are free downloads. They detail "how to" diagnose and repair most everything about the car including the electrical. I don't recall seeing "how to" for entire dash removal in those manuals.
The wire is the pipe that the current travels through. And like plumbing, it's rarely the root problem. The plumbing fittings are just like electrical connectors, the plumbing fixtures are just like manually operated electrical switches, being the root problem 99% of the time. These are the items that plumbers, like dealership service techs, will service. A plumber wont pull all the pipe out of your home. A vehicle service tech would not remove all the wire from a vehicle.
Where the harness connectors attach to the printed circuit boards on the instrument panel is the perfect example of, "It was fine before it was disturbed". Like some pipe fittings, laying hands upon it did more harm than good. The sad part... Whether you pull the entire dash or the instrument panel only, you will lay hands upon those "fittings". Good luck either way.
I must add this... I find it puzzling that some owners will buy a entire new under dash harness and attach it too all their same old switches.