What specifically makes the late Dart Sports/Dusters so much heavier?

Glass is heavy too. The Dart Sport and Duster back glass is bigger. All that stuff mentioned earlier and the glass adds up.

Yeah, I should have been more clear, I just meant to compare the 108" wheelbase family to each other. I already have 2 111" cars, thinking the next one should be a Duster/Demon/Dart Sport for a little variety. The wife will still say they all look the same, but we know better.