They're used. They got removed for a reason. Did you inspect them or anything before you bought them? It's hard to determine whether you got scammed. How were they advertised? Were they advertised as tight and smooth?
New regulators don't have slop in them. They're just loose enough to alow the arms to rotate smoothly. GM's cheezy metal arms and materials plus 10,000,000 cycles over the years will wear them out.
You may be able to tighten them up. Take them to a shop. They may be able to crunch down the pivot pin some more in a press to take some slop out of them. Don't go crazy on them- keep in mind the cheezy materials. If the hole in the rotating arm is wallowed out, though, then you're probably fugged.