Joe,
There is a hidden lip that tucks under the spoiler shape and it's attached with 6mm bolts that are provided. The wheel well faces can be removed or attached with rivets if you use it. Sometimes the lower fenders have been modified to fit deeper dish wheels so the spoiler was designed to fit un-modified or modified openings. You can see the hidden lip and mounting holes in the close-up. It does fit all years but I am not sure how well on very early hand-built 71 cars---never tried to fit one. All customers have reported a very positive no issues install with very good fitment. I spend allot of time build my master designs making sure they fit the car as good as possible. Hope this helps.
Kirk
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