"Stock 1990 gas tank - 15 gal.
I could swap out to the newer (1993?) gas tank that I believe is 20 gal (IIRC it would be about 4 or 5 hundred - new purchase - unknown if I could find a junk yard tank).
Extra fuel is a rare need so, financially, I should just stick gas cans in the jeep - lol."
I'd go for the 20 gal upgrade if you have an any 'excuse' to do it - say you need to drop the old tank for some reason etc. Maybe because my OEM tank is only 10.5 gal, which is tiny, I really felt installing another tank was the way to go, as even with a 5 gal aux can, I still only had 15. Mounting the second tank gave me an additional 15 gal for 25 total, and now its never really an issue. I have the aux can rack i made for my spare tire in case I am ever really concerned (the old carb v6 isn't the most fuel efficient), but I think now its more useful to carry a 5 gal water can for some desert trips. Obviously water isn't something that has to be outside the jeep, but given the limited 'inside' space, it helps.