Scoop....
I am enclosing a photo of the spoiler installation from the 1967 Camaro AIM. There is no sheet for this installation in the 1968 AIM but they did insert it into the 1967 AIM even though they never installed a spoiler in the 1967 Camaro. In this photo you will note that they show the use of sheet metal screws to attach the spoiler and they also indicate that you need to drill the holes in the valence for the screws and, according to other owners, theirs was done this way. But....that was not the situation in my 1968 07C build Z28.
If you will refer to the link that Marty included in the above reply, Please note post #20, in which I state that my Camaro had the machine screws with the corresponding nuts. And in post #25, I supplied, to the best of my knowledge, the information to obtain the hardware for the spoiler installation.