73 dart not cranking
Review the MAD article.......
http://www.madelectrical.com/electricaltech/amp-gauges.shtml
and the diagram on that page
The ignition switch, the "hot buss" in the fuse panel, and the headlights all get power from the welded splice in the black ammeter wire
If the headlights are good and bright, but the cluster won't come alive "with the key," and won't crank, then it's more likely to be the ignition switch connector or the switch itself.