The Arizona Dart - teething.

This is a BBD carb, but the throttle linkage is very similar. There are 2 idle speed screws....1 works with the fast idle cam (which yours is correct), and the other is the curb (warm) idle. It bears on the end of the big screw that holds the fast idle cam. It looks as if yours has had that large-headed screw replaced with a small-headed one. See pic below...