How to test fuel sender

I usually get decent results by joining ongoing conversations along the same vein as my issues, rather than reinventing the wheel. We drained the tank and removed it because the sending unit would not clear the 8-3/4" rear end. The sender was replaced, fuel tank reinstalled, and at least 8 gallons of gas were put back in. The ground strap was tight and a secondary ground was added just for good measure. With continuity of the gauge wire confirmed, and the resistance range of the sender within reasonable tolerance, what else could be the problem other than the gauge or voltage limiter?