Not sure it this is what you are looking for. If so, I found hanging the air dam from the fender extensions with long studs helped me position for the small bolts.
I can tell you what I used, do not know what the factory used. First of all, I glued heavy rubber electrical tape to the edge which meets the lower valance flange in an effort to limit paint damage. I used standard 5/16-18 clip nuts and typical washer equipped body bolts. I used 10-32 stainless hex bolts, nuts and washers for the small hardware. Easy enough to get at the nuts. Suspect GM used clip nuts for the small hardware but I could not find any deep enough. Finally, I installed the masticated air dams before installing the lower baffle. I was lucky enough to have all six of the original clips in perfect condition. I believe there is a clip for something on a Mopar that is close. I’ll have to dig up the number and manufacturer.
