[OG68]

[QUOTE=Verdoro 68;6592724]Mine are 5/16 headed screws with the clip nuts on the valence. I think they're original - at least they've been that way since I owned it - but who knows what happened before./QUOTE]

I think yours are correct Ken. I checked the 68 and the 70 MPCs and strangely enough there is no mention of the 68 parking light fixture for the 68 B and A bodies with the exception of a U shaped 10-16 nut, PN 9789424, to retain the housing.

There is however a line for the Firebird mounting screw. 10-16 x 1/2" Hex.
PN 9419303

Cross referenced to the AMK catalog and came up with this;

9419303 Screw- https://www.amkproducts.com/search-result/?ser=9419303

9789424 Nut - no cross reference to AMK

From Ames; https://www.amesperf.com/parts/25273/