66 Dart gas Gauge

First requirement is a working limiter... Even though not using the temp gauge you should still have that purple sender wire. If the limiter is working your meter will show a pulse voltage on this wire with switch on, 2.xV, 3.xV .
You can find the fuel sender wire (dark blue) in a harness connector behind the left kick panel. Same pulse voltage should be found there. Short it to ground. If gauge is good the needle will move to max full.
If the limiter isn't working we'll figer out why not.