evac34,
You say that you hooked the gauge to the positive of the battery...does this mean the gauge is out of the truck? The case of the gauge needs to be grounded too.
Your wiring should be; power to fuel gauge. Wire from gauge to sender. Body of sender AND case of fuel gauge hooked to ground. Try that, but don't blow yourself up!
The electrical forum would be a great place for your next 'juice' question.
Stuart