John, Hold on for a moment. Let make sure you do it right as installing/removing a gas tank is a large pain. Make sure your gas gauge is suppose to see 0-30 ohms (mt to full). Go out and buy a 30ohm resistor at "Radio Shack". Less than 2 bucks at best. OK, take a jumper wire with alligator clips (buy several if necessary). Clip one end of the jumper to the end of the sender wire and the jumpers other end to a clean frame ground on the truck. Turn the key switch on. The gauge needle should come to rest around "E". If it goes to "F" or anywhere else there's a problems. If you read what you want, turn key switch off. Remove alligator clip from frame, clip that end to one end of 30 ohm resistor. Take another jumper wire and clip one end the the other side of the resistor. Clip other end of new jumper to same frame ground. Lay all this on shop towel or something to keep from shorting out. Turn key swich on. Gas gauge needle should move to close to "F". If it doesn't then you have other problems. Let us know what you get and these guys will help. Good luck.

Six volt guy living in a twelve volt world