You probably won't find a new one because your truck has the narrower frame. What I would do is take some measurements of your opening and look at websites like gastanks.com and see if you can find a tank that's narrow enough to fit your opening. I know on the highboys (narrow frame) people have used Bronco II tanks. And the other option would be to get a new tank for an F series truck and see if a welding shop could cut out a section and then reweld it making it narrower, but you'll probably end up spending much more than just trying to make a tank work.