So the real reason the Brat had seats in the back was to avoid the chicken tax on imported small trucks. I think the intent was buyers would remove and chuck the rear seats. Though growing up,I saw many of them with seats still in place. The chicken tax was a set of tariffs on various foods and light trucks from Europe. Most of the restrictions were lifted except the light truck tax. Most manufacturers worked around it by importing incomplete vehicles and final assembly here, or classifying them as passenger vehicles and installing cheap throw away seats.