Based on the door frame, the cab might be an 88-98 (maybe even 99-07!)... the bed is definitely a 67-72... somebody really need a bed for that truck and which one didn't matter!
If it really is an 88-98... not many longbeds were built for those years... it *could* be a shotbed, but you'd have to contact the seller (but it does appear rather long in the pics...) The tailgate looks really beat up. The area below the taillights has also taken a smack on both sides too. I'd want to see the rest of the bed before you get too excited.