Sorry this took so long. I was out of town for a few days.
This mount is from a 91 Firebird. Originally, the mount was bolted to the sub-frame on the car. If I could have bolted them to my frame, I would have, but I had to cut that part of the mount off to push them out a bit.
If I were to guess, I'd say every 3rd gen Camaro and Firebird equipped with a rear swaybar used these same mounts.
I tried to post pics, but they didn't want to keep working.
Here are some links instead.