I adjusted my Autometer fuel level sending unit and have had good results. I had mine stick a few years ago and it was not accurate either, so I found some instructions from Autometer that I used to properly adust the float level and cured the sticking problem while I had the tank out of the car. There have been no problems since, and I have not run out of gas.
Here is the link to the instructions.
http://www.autometer.com/productPDF/421B.pdf
Hope this helps,