Leaf springs for dart swingers.

GreyWizard said
I had not noticed that before. I knew the 74+ Swingers were different in the back but did not connect that the bumper was lower.

Yea the bumper actually sets under the taillights. If you look at the quarter extension the 74-75 taillights are in the same spot as the 73 but the bumper is under it instead "over" the taillights
That's not the best picture of the bumper but the other one I have wont upload for some reason