The interior volume is about 3085 liters, which would hold about 815 gallons. The Laredo also has a 20 gallon fuel tank. Add about one more gallon in oil capacity, 4 more gallons in the cooling system capacity.
You could fit a total of about 840 gallons of fuel into a Jeep Cherokee Laredo, which would cost a little over $2500. The fuel will leak out of the interior, though.
Of course, if you actually want to drive it, you can only put fuel in the gas tank, which is 20 gallons and about $60. Assuming you refill it when you're down to a quarter tank of fuel, you can expect to pay around $45 per fill up.
Once again, the trash in the bottom of the tank myth pops up. I can believe there's some benefit in cooling from keeping the pump submerged, but the constant changes in acceleration are going to keep sludge, trash, dirt, etc, from settling at the bottom of the tank. Any foreign junk in your tank is going to get thoroughly mixed throughout your fuel, which is why: a) Don't let dirt and other debris get into your fuel tank b) Why your fuel pump has a screen filter to prevent any junk that does get into the tank from entering the fuel lines.