I had a long range tank,but wasn't from MAF. On mine I took the sending unit and placed it against the side of the tank (tank was out of truck). This gave me an idea of how the long the arm needed to be extended. Then I snipped off piece of a coat hanger, cleaned, and brazed it in place. I'm sure a lead free solder would also work fine. You can adjust the length so that you still have a couple of gallons when on empty. I had a ground problem though with the way the tank was originally mounted and didn't like it being low (flush with the bottom of frame rails.
If you have never brazed before, it is easy if you have a hot gas. Otherwise, the solder meant for plumbing copper pipes and some map gas would work great.