440six:
Your brackets are the correct 1971 brackets, but your trunk lid has the holes for the 1970 spoilers: either the 1970 wing (that big "comma-shaped" hole) or for the AAR lip spoiler (the smaller square hole to the left of it; there should be, I think, a total of 4 square holes to mount the AAR lip spoiler).
By the black coating on the lid, it looks like one of those reproduction lids sold from sources like Year One or The Paddock. They will not mount the correct 1971 spoiler.
I hope this helps gets you straight.