Pull the tank! Find a good radiator shop with experience boiling out and re-lining gas tanks. Should be less than $100 for a clean tank with an anti-rust alchohol resistant liner. Look over the sender unit. it may need to be replaced or repaired. If the bottom of the draw pipe is rusty, you could splice a repair piece to it. One of those small outboard type gas tanks could get you around in a pinch using some hose to splice to the fuel pump.
You won't regret having a clean tank.
