I recently bought a 87 firebird project (not running, been sitting since 2002) and when I was messing around with it, a small acorn looking object fell off under the rear passenger side wheel area. Can someone please help identify what it is and what it does? Thanks.

 

sway bar end link-kind of common for them to rust and fall off in road salt usage areas.

 

That's it, thanks!

 

You might want to have an experienced mechanic look at the rest of the underside of your car for other rust damage.