The heads of the bolts have a rectangular strip of steel attached to them acting like a spring. (to hold them to the tail panel)
These are repopped, you should be able to find some picts online. Look under tail light bolts - 67 firebird.
There is a round hole in the tail panel with a horizontal slot. You press the head of the bolt through the hole, then slide horizontally in the slot. The spring holds them tight. Then you place the light assembly over the bolts and install the speed nuts over the housing.
I used to be indecisive. Now I'm not sure. I feel like I am diagonally parked in a parallel universe. 1968 400 convertible (Scarlet) 1976 T/A - 455 LE (No Burt) 1976 T/A New baby, starting full restoration. 1968 350 - 4 speed 'vert - 400 clone (the Beast!) 1968 350 convertible - Wife's car now- 400 clone (Aleutian Blue) (Blue Angel) 2008 Durango - DD 2008 GXP - New one from NH is AWESOME! 2017 Durango Citadel - Modern is nice! HEMI is amazing! 1998 Silverado Z71 - Father-daughter project 1968 400 coupe - R/A clone (Blue Pearl) (sold) 1967 326 convertible - Sold 1980 T/A SE Bandit - Sold