The plastic nut picture is poor, so I am attaching a better one.
Note the nuts pictured have 4 segments that expand and are probably intended for a square hole.
There is also a 3 segment version that will work, but it looks like it was made for a round hole.
After watching some headlight repairs on Utube I wanted to post some comments.
I do not own a Firebird..... I am the Buick Club of America technical advisor for Buick Reattas and
have repaired a lot of Reatta headlights. I also repair GM power antenna and have done several Firebirds.
I recently stumbled on some Utube videos of people showing how to replace the headlight motor and a couple that show repairing the motor.
I have lots of experience with Buick Reatta headlight motors, and while it may be common knowledge here, I am new here.
*I noticed several motor repairs...