Check out this baby. 1970 e-bay Dart.
My bad, I should have said
'72/up, sorry! I also should have been more clear, it's a '72/up
Scamp bumper.
1970 and '71 jacks grabbed the bumper from underneath:
'72/up jacks had a hook which fit into a slot cut into the bumper under the taillamps (much worse design, IMO)
Hence, the bumper on that car was replaced and is not original. What's more, if you get a flat rear tire you're screwed, because you don't have the correct jack for that bumper!