Where do I find it?

Everything on the car is chassis grounded. The fuel sender is isolated from a chassis ground by the rubber seal between it and the tank and also by the rubber hose connecting the fuel line. In other words a properly installed fuel sender is no more grounded than it was in the shipping box.
The factory installed a snaped on metal jumper over the rubber fuel hose connecting metal to metal and completing the chassis ground path.
Hope that splains it :)