Can I install a new fuel sender unit on a 72 duster without removing the tank?

Can you tell where the leak is coming from exactly? Are you sure it's not the filler neck where it goes into the tank?
You are better off pumping the tank down into containers rather than burning the fuel.
Good question. I really don't know as it was getting dark when I fillied it. I was talking to a guy who pulled up to admire my car just as I finished filling the tank. While I was talking to him, I noticed fuel leaking from around the tank. I looked under the car and saw that it appeared to be coming from more than one location, but I coulnd't be sure. At first I thought my tank seams were leaking but it was hard to tell. I probably leaked a good cup or two of gas on the ground. After I got home I started searching the forums for clues which lead me to believe the sending unit might be leaking. Tomorrow I'll crawl up under the tank and take a closer look so I should have a better idea where the fuel is coming from.