These tanks come that way. My suggestion is to send them back and make sure you get your shipping back for both ways. If they (any vendor) want to fight you on that ask them if they sent you a replacement if it would fit with no problems, Most of us know that many aftermarket parts need a bit of massaging to get them to fit properly we understand (to a point) but I do not believe that a fuel tank should ever need this. There is too much to loose with safety and liability.
Mike Taylor