73 dart seat frames??

I am restoring a 73 Swinger for my daughter and I ordered at set of seat covers from legendary. What they sent me for the rear top seat does not fit my frame. This car is very original and I have no reason to believe that the rear seats have ever been changed, plus they fit and bolt up perfectly. Legendary insists that I have the wrong frame. It has a tag with a part number and a date of 2/14 73. Does anyone out there have a part number from their reat seat? I appreciate the help.