1975 Dart sport convertriple

I know this probably is not the right spot to post this but if anyone knows anything about this I would apprecite some input.
I just looked at a 1975 dart sport convertriple. Slant 6, 904 automatic, original air car. Nice piece. My concerns are, it has fiberglass front fenders and complete fiberglass rear quarters. The rear quarters go all the way into the trunk lip so it is not just a panel. I've looked online and have been unable to find anything about fiberglass quarters. Could this by chance be a special concept car by dodge or do you think somewhere fiberglass quarters where produced after market. The current owner bought the car in michigan 15 years ago and doesn't know any history.
Thanks for any input.
Idk if this Is active at all 10 years later but I bought that car it was my first car at 16 and I still have it to clear up the fiberglass quarters they are almost an inch thick of bondo with 2 steel panels over each other