When AOSmith made fiberglass parts for 1968-1969 Shelbys they did it in a very specific manner. The parts should be smooth on both sides. If you are seeing "kitty hair" or fibers, most likely its been repaired or is reproduction.
I thought this might be helpful in light of a recent discussion on BaT
http://www.thecoralsnake.com/FRP.html
I have been asked to post some pictures of reproduction fiberglass. coming up....
Notice the fibers in the underside of this hood. Its a reproduction. Tony Branda sells these for $1464.
(https://www.saac.com/forum/gallery/8-270224191603.png)
Same here, not even close to the original texture.
(https://www.saac.com/forum/gallery/8-270224191639.jpeg)
Reproduction lower scoops. Branda price $140
(https://www.saac.com/forum/gallery/8-270224191656.jpeg)
These upper panels were originally made of steel .
(https://www.saac.com/forum/gallery/8-270224191714.jpeg)
If you need help identifying original fiberglass (FRP) please ask the forum.
Dave sent some additional pictures, which I can post later.
Original scoops from Dave. thanks...
Note pink fiberglass (bottom) and thickness of part compared to reproduction above
(https://www.saac.com/forum/gallery/8-280224140113.jpeg)
"Thanks for helping me avoid a BIG mistake" -Bob H via email
Hope to have more NOS pictures this afternoon
Here is a pair of NOS fiberglass scoops. As my friend, Mr. Perkins always says,
"Reproduction parts have no collector value!
Remember Genuine Ford Parts Are: "Made Right", "Fit Right", "Last Longer" and make your car more valuable!"
https://www.ebay.com/itm/334989940601?itmmeta=01HQVBDZ0H3G9MAHJNKA8EEXMF&hash=item4dfef4d779:g:HMAAAOSwZXlk27F6&itmprp=enc%3AAQAIAAAAwGxC6MNI7Q3IoOnRmR9h5hV0%2B3qZsVE4kb5xirZ3XajqWkbVQOAkLgTAXwP9PdWJYfe4iHRGkBEJMaF2rLTDVpND4Sip%2BJVwiyaX2tWSZf%2FjgqoYuBqBRsF7GafTe3NHz49C9FP2BVb%2B6f8F6Q0eVfs4bembh14TdxuTTVgXNFXqjPQWe9dAOstdm%2BNk5earyqPhL4aUSp14ixfmrnJ28XVxYoSC2MS1tBsVmlwsjfCCCYa%2Frfb7%2BAjHSF8CpNkqjw%3D%3D%7Ctkp%3ABk9SR7rwt-u-Yw
(https://www.saac.com/forum/gallery/8-290224161722.jpeg)
(https://www.saac.com/forum/gallery/8-290224161739.jpeg)