I believe you should be able to submit a car MODEL to the marketplace, as long you, as mentioned already, specific that it’s only a mesh and not a functional object.
That said, I would recommend that you, or get someone else to do it for you, get it setup and made interactive, as it would make it more likely that people would buy it. Remember that a lot of people are just like you, who just want something they can place in a level and work with fast.
Then again, if your car model is just used as a prop, I guess its fine just having it as a model, but the more you do to make it easier for others to work with it, the better.