Prolly have to order them. I ordered a front tank for my f250 from rockauto a year ago but they sent me an f150 short tank so I ended up just cleaning out the original. Lol I still have the wrong tank in my garage taking up space. Just double check what you order so you get what you need when you need it.
Also if you end up needing to replace your filler hose/neck and your auto parts store doesn't carry one (my situation) just find the closest shaped radiator hose and trim to fit if you find yourself in that situation. When I pulled my back tank the filler neck broke off about 4in from the filler bolted to your bed side. Good luck with everything. If you find the bed bolts to much to handle the tanks if close to empty are not that bad to drop from the bottom. I did mine by myself with no ******** involved just watch your head when it falls and getting to your fuel pickup line and return if dropping it from the bottom is very easy just pull the plastic clips and slip off the hoses. Hopefully you will be able to pull your bed like you want but if you find you can't its easy taking plan B.