Auxillary Fuel Tank ?

Transferflow

Yes, there are several different brands out there, with prices all over the map. They aren't as common as diesel auxiliary tanks, but they do exist. It would probably be easiest to google "Auxiliary gasoline tanks". You should get a lot of hits, and decide where to go from there.

I have a 36 gallon tank for my diesel and it is wonderful. Very much a worthwhile investment IMO.

We installed a Transferflow aux tank in our '99 F250 V10. At that time, towing our fiver, we got 9mpg. It stopped at every gas station. The aux tank helped, but we eventually traded in our current truck.

If Transferflow does not make an in-bed auxiliary gasoline tank (that pumps directly into the truck's main tank), they do make in-bed refueling tanks. Not as convenient as an auxiliary tank, but they give you the same additional range.

I prefer not having an auxiliary tank so I have to stop every 200 or so miles to get fuel and stretch my legs.

When I was younger we would drive for 8 hours with fuel stops as needed. Now that we are older we try to limit our daily drive time to a maximum of 4 hours and usually hit 2-3 hours a day. Makes for a less stressful towing experience.

As others have indicated there are many options for auxiliary tanks or larger primary tank.

It's sure good to stop and walk around for a bit, it really makes the trip seem easier as we get older.

Second the post above to use Google and decide where to go from there.

FWIW, although diesel, I had a previous truck with a small-ish tank and a big 5th wheel. It was not a problem stopping, as per others, about every 200 miles....but we got an auxiliary tank (125 gallon) anyway. The biggest benefits were: a) if we wanted to stop every few hours we could, but we didn't have to; and b) with about a 1200 mile range between aux and factory tanks, even if we wanted to stop a lot, we never had to fuel during the day and could top off in the evenings after we parked for the night and no longer had to worry about maneuvering through the stations with a 39' 5th wheel on the back.<<<< that was worth the price right there.

Titan Fuel tanks... I have a 51 gallon that is sitting in the same spot that the original tank was sitting in under the truck

X2 on Titan. 500+ range. Took a little while to get used to the fill up cost.

Did any of the trucks of that year come with a bigger tank? If so you might get a good deal at a junk yard. If not that, I would second the titan suggestion.