The July 1973 and August 1973 issues of Four Wheeler Magazine included these two ads for fiberglass racing shells. I’m not sure when World Plastics began advertising in the magazine, but I doubt it had been for very long. The ad on the right shows a full-body size flat fender shell, while the ad on the right shows a narrow body shell (both Bobcat and Parkette also produced racing shells).
I don’t know how long these were offered, what happened to the shells, or what happened to the World Plastic’s company.