Its probably not the place to post this reply in a wanted section - but SMC is a process not a material - SMC used by GM is fiberglass used in a molding process with heat and tool pressure to distribute the fiber's and resin , the fiberglass material is termed a charge used in the tool die.
Corvettes are made of SMC panels which are fiberglass , not to say materials other then fiberglass cannot used in A SMC process tho.
I think the aftermarket parts are made with a more traditional hand laid fiberglass sheet process - but thats just a guess thinking the aftermarket would not invest the money in a compression molded fiberglass tool.