I believe that any original parts for that era trucks would be gold. Condition is everything, however. Considering that
just over 10,000 Cameo's and far less of the GMC version were produced, they are certainly rare parts.
I have not had any occasion to work with any aftermarket fiberglass components but many of the aftermarket
metal body components are far less than stellar.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine