Even though you probably never heard about it and they never offered it for purchase: Ford Motor Company under Henry Ford actually developed a car purportedly made out of hemp.
In real life, the car was made using hemp among other materials, instead of being simply made “out of” hemp. But when reading the initial description of what was used in their biopolymer car it does seem that hemp could likely fulfill the need for cellulose and resin more effectively and ecologically than pine.
So Ford did create a plastic car using hemp, but his design did NOT have the car being made 70% or 100% out of hemp. But now that we have even more sophisticated polymer technology: it is seriously possible to create such a car.