Yes, it can be added to older models. I inquired about it but the price was too high to make the conversion. Besides, we like having the storage in the rear hatch for our 2007 400SS. The price I was quoted from Formula back in early 2018 was over $15K (part number 1336338TAGKIT for 400SS engine hatch and seat assembly). This includes all of the upholstery (foam and vinyl skins) with mounting hardware. It's basically everything you need for a complete replacement made in the same color gel coat and vinyl. They are built to order.