It's always been my belief and observation that early trucks had no ground wire to sender. They relied on ground contact thru sender screws to tank and tank touching frame. So when someone had trouble, we advised to add a ground from screw head to frame. Later years there was a tab on the sender for a ground wire. I don't know what Chevy "engineers" thought when sender has a gasket and tank had cushions under tank straps. I do not know exactly what AD had or did. My experience is 55.2-66 and up. The steel gas line would possibly ground the sender on it's way to fuel pump, at a line clamp somewhere, but it had a rubber hose near outlet.
Bottom line: Waveski's question is a trick question
Yes, the tank needs to be grounded to ground the sender. Other than that, no it does not. As everyone knows, the tank is hard to ground and maintain todays good idea to re-pad the straps/add cushions/whatever. The sender itself has a gasket. Small screws are not a super way to ground. Hence the newer truck's senders have a dedicated tab built in. So if you don't want to have trouble, ground the sender flange by adding a wire from a screw to the frame and don't ask questions.
(second smilley face is non binding)
This is what Carl said in a much more friendly way and a lot less words.... and a lot less coffee.
