Mike,
I looked thru my pictures and found a few of screw 9419380. This screw is detail 12 shown on page 147 of the AIM, UPC Section 11/13 covering the radiator and fan shroud. Other than my '69, all the pictures shown below of that screw are from various survivor '69 Camaros. I got my original screw from Larry Christensen along with a number of other original restored parts from him during my restoration. All the screws I have seen so far are indented head with "LG" head marking, encapsulated washer, 1/4-14 x 3/4 long. At one time, AMK Products carried them as #9421985.
The first pic attached below is my screw. My '69 is an 05A Norwood build X33 RS Z28 (restored)
The second pic is from base '69 Camaro Norwood build 10D survivor.
More pics to follow...