Fuel gauge ground!?

Chassis ground is a metal to metal path. Like everything metal becomes wire. That probably dont make sense to some of you either. Anyway...
The gas tank probably is chassis grounded given how it is straped in. The fuel sender is isolated by rubber both by the fuel hose and by the sender seal. The factorys little ground strap is a simple way to complete the chassis grond from the sender to everyhing else chassis. The metal fuel line is chassis grounded by all those hangers along the fuel rail.
Now if we hunt another place where the chassis ground could be broken we find ourselves back at the chassis to engine ground strap to the firewall. That has to be in place to complete the chassis ground side of the circuit across the engine to the ground cable and on to the battery. Am I helping at all ? I'm trying :)
Heres a quick test or fix to try... take any piece of wire (even coat hanger) and install a jumper from the battery ground post to the radiater support. Factory installed this same jumper on 73 and up models in addition to the firewall strap.