[In The Ten Ring]

Actually it appears as if it had EEC (evaporative emission control) at one time but someone capped it off. (There should be two short snouts at the base of the filler neck, connected by rubber hose, to (I assume) recirculate fumes back into the tank). If that is the case, then it's a tank from a 1971 to 1972 truck. *If I'm wrong somebody correct me.

Worth? That depends. If someone wants to keep the gas tank located in the cab and behind the seat then it's worth whatever someone will pay.

I removed my tank last month, had it renewed (rust cleaned out and coated inside) for $238.00. The stuff is supposed to last forever and by using the old tank I took out any guess work on quality and fitting the old mounting holes. The guy who did the work said my "tank is in excellent shape, other than the slight coating of interior rust and much better than many tanks he's fixed"....so I would think if your tank is solid (not rusted through but even if it was it could be fixed) and someone wanted to use the behind-the-seat tank, then it has value. I cannot guess how much as I don't have experience in such a tank's market value.