1969 Shelby grill attachment

Hi. I removed my front grill from my 69 GT500 to refresh the paint. I want to reattach it and see no type of nut for the top 2 attaching bolts! There is just a plain hole on the headlight assembly. Can't get to it from behind or underneath. Took out the headlight and no access from there. Anyone know what the nut is supposed to be? In the factory diagram, there is NO nut! (see attached photo) Thinking of using a U type speed nut, but haven't found one with a long enough reach.