Looks rough. What is the tank in the engine compartment?

“I have a 1960s Kaiser Willys Jeep for sale. I am unsure what year it is but have provided pictures of the serial/model number It has 4×4 and a 4 cylinder in it. I do not know a lot about it other than it has a newer battery, alternator, exhaust, and muffler on it. It does not have a title. With a little work would make a great mud toy. I am asking $850 obo or may be interested in trades. ”

http://stlouis.craigslist.org/cto/5872233697.html