Have you tried to blow air back to the tank? Should hear bubbles unless it's clogged. Also they make better rubber hoses these day that wont deteriorate like the old ones because of todays gasoline. I just bought some from Rock Auto. It cost more than regular hose, which is ok for anything else but gas. The tank size I can't explain that, but it only makes sense to me if it was maybe a tank from a 77-78, because that's when they made a total change to the rear deck height and gas tank area for the EPA gurus. I know they made some changes to the 260 half way through, which soon became the 75-76 280. (image a smiley face here shrugging his shoulders)
