it depends on what type of wheels you have, dayton-centerless wheels are attacched with wedges and clamps, you would need to install an empty wheel to clamp the good tire on so why not just carry a spare, it doesn't need to be a good highway tire, a roller or maypop would ork to get you to help.
a 6 or 8 ton jack will have sufficient capacity to lift a skoolie, but the 12 tons are generaly a lot beefier and have a larger more stable base.