73-76 Duster/Sport folding seat conversion??

Has anyone converted a 73-76 Duster/Dart Sport from a regular rear seat, to a folding rear seat? I am still debating whether to go with the folder or not. I was curious about what to expect in the change over. Are the sail panels the same for both? Is there a gap between the rear seat and the package tray, and what fills it? What other trim issues would there be? Do you need to change the filler neck? What is the going rate for a good core, and all the components? I have been slowly picking up black interior parts to redo my 73 Sport's interior. I've gotten most of the trim I need except for the new white door panels and seat covers, and black headliner and carpet. Sorry for all the questions, but I'm the type to get as much info as possible, and then make an informed decision. Any help would be greatly appreciated. Thanks, Tim.