What is this? '75 Dart Swinger

Google has failed me with this car, yet again.
Was taking the '75 Dart around for a spin, hit a bump, and a god awful "squeaking" sound has ensued. Thought it was a strut or control arm, but nope. This little knob is hitting up against the frame. Can anybody identify it? Just need a name to know what I have to replace.

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