NUT, Hex Flange Stamped, thread cutting
PN 9419753
1/8 HX FLNG STAMPD NUT 5/16 AF .53 D BLK ZC. 10 pk
Source AMK part number B-10629
Now this might be close, the trunk Nut likely had sealer and carried a different Fisher (GM) PN
The pins on the Header and trunk 68/69 emblems are small and I think going off memory they are smaller than say a 8-32 machine screw thread.
Others have better catalogs and parts books and will chime in also.