There are different necks, the '73-'78 has a round bolt-on flange that bolts flat on the bedside & the '79-up has a different one for the use with the pocket/filler door. It sound to me you have the old one bolted in the pocket, which would make it too long & tilted down because of the pocket. From what I'm making of it you have a "new" bed with an "old" filler neck. As mentioned, the tanks are the same. Sounds like you need a "newer" neck. Lorne