how to bench test a 70 Dart instrument cluster?

On my 65 coronet, ten years ago, I was having all kinds of electrical gremlins that were causing crazy issues, especially with high humidity. After many hours of testing I tracked it down to the original printed circuit board. I confirmed it being the problem by removing it and replacing it with a custom made wire harness. Right now I'm in the process of making a custom wiring harness and updating some things. I plan on replacing the printed circuit board with a new one, now they are available.