Before I crawl under the dash

I am just getting my 70 Dart GT running. While it was apart I rebuilt the entire dash and gauges, assuming it's a lot easier to do out of the car, and because I had a bunch of non-stock wiring to accommodate and I wanted it to tuck up and be wired properly. I bought new temp and gas gauges from Hoffmans. There is a completely new wiring harness through out the car (M&H), and the sending units for gas and temp are new, as is a transistorized voltage limiter. Neither the gas or temp gauge move at all. What are the potential problems that I should be looking for when I crawl under the dash?
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