These used to be more popular during the 1970's. A Volkswagen Beetle, and several other cars, would have the body lifted off, and a Fiber Glass Body was put on there in its place. These were sold under various names, such as "Kit Car", "Fiber Fab", etc. One method is to get something rough and similar and sculpt it into a custom car, or a clone of an expensive car. It takes artistic talent to be able to do this, either Vag 15.7 that, or a giant CNC Machine. One method used Chicken Wire to make a skeleton structure with Fiber Glass placed on top. Another method used "Fiberglass Over Foam Method". Since you want it fully built and ready to drive you might have to get someone to build it for you.