forget the alt fuel kit....bug them to come up with a larger capacity light weight plastic fuel tank.  my tracker would get awesome fuel economy if it's tank were bigger than a milk carton.
Shoot, if you have a 2-door, and you have a body lift, there's plenty of room to put in a tank from a 4-door, I think, plus raise it as well.
2-door:  11.1 Gallons
4-door:  14.5 Gallons
If that's not enough, go to some place like
http://www.summitracing.com/ and order a fuel cell, that'll fit between the rails...