Best thing IMO would be an auxiliary fuel tank. I think there are bolt-on gas tanks for some applications but I don't know which ones. Many US-market vehicles have what are, IMO, pitifully small gas tanks (my 1st gen Taco and 3rd gen 4runner being examples of this.) You ought to be able to carry an additional 10-12 gallons of fuel in the space that was occupied by a full sized spare tire, and that can make a huge difference. Certainly I'd rather have a spare 10 gallon tank than have to find a place to strap on 2 5 gallon cans. It's also safer and more convenient to have the fuel in a tank rather than in a can.
Downey (now defunct) had a aux tank that kept the spare in the stock location. Honestly I like the spare in the frame rails, keeps the center of gravity low. A 33" tire
and alloy rim is roughly 75 lbs., plus doesn't take up precious cargo space, which is premium real estate in the tiny Tacoma/4Runners. :ylsmoke:
I always liked the old Ford trucks for carrying fuel, 19 gal. tank behind the seat, 20 gal. side tank, and a 35 gal. third between the frame rails.
That is a hell of a lot of range, even with 10-12 mpgs those old trucks got.