Re: Replacing rear control arms - lowers question.
I see the pic of your rectangular arm. It appears to be collapsed around the bolt hole as if it were boxed with a piece of flat strap. don't see anything that looks like a internal support to keep from collapsing the arm when tightening up the stabilizer bar bolts, which is why I posted the link to the real part.
Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.