73 dart 4 door trunk seal weatherstrip troubles

my seal does not install like that at all. and I believe it to be original as the car had only 60k on it when I bought it. mine is shaped like that one, but the surface being used as the seal in that photo is the glued down side- there is a ledge running all the way around above the water channel. it is definitely unique to the four door and possibly the swinger, the sport trunk is obviously different.