I know that the 70 and 71 models came with different rear valance support brackets, so there are differences between the two model years. What I can offer is what I know about the 71 Barracuda. I have two "one owners". Both have the same hardware and fasteners for the rear valance. Your pictures are of the top corners, correct? I have attached a couple of pictures of what I have at those positions. These are the originals, not reproductions:

(A) These are located in the top corners at each side and attach the valance to to the quarter panel. They are sheet metal/self tapping type pan head phillips head screws. They have a captive washer and thread into the U-clip that is pictured.

(B) These occupy the next two slots down along each side and also attach the valance to the quarter panel. This a three piece setup with a stud, U-clip, and a nut with a captured rotating washer. You should have a total of four studs, four clips, and four nuts. These too are the originals, not "repros".

David