this probably won't help, but there are some very nice rear tire carriers out there that can hold fuel as well.
Inside storage - If you need to keep the rear seat it can be tricky, but maybe the rear drawer from Tuffy. They have two. One mounts under the rear seat (obviously not THAT much room in it, but a very efficient use of space) or their regular rear cargo drawer (that is what we use and it is really nice. Tons of room in the drawer, and on top of the unit) However, you can't keep the rear seat with this option though.
In TJ's we have to get creative. Although in all fairness to the Willys and CJ guys our TJ's are HUGE!