If you're talking about making a car from scratch, there are a great many programs that can do that. They often look about this complicated:
(Autodesk Maya 2011)
It would be a gross understatement to say that it's quite complicated to take drawings and turn them into 3D models.
Typically car designs that go from drawing to physical finished car go via the stages Concept Art to the design orthographic on paper (blueprint), to a clay and plastic sculpture, which is then scanned with a 3D CAD Reader and projected into NURBS in order to be cleaned up. (The NURBS model is then used to program manufacturing equipment). Cars as they appear in video games are Polygonal models which are usually modeled by eye and far less accurate than the real thing, but inso are far more flexible in terms of geometry customization. Regardless of the route taken to achive a 3D model of a car, Rendering them is incredibly easy once sharers have been set up.
But if you're talking about a program specifically made to edit the appearance of cars by presets, I do not know of programs that do that. I wouldn't say they don't exist, I just don't know what they are. It would be easiest to simply use the customization options in racing video games, such as Need For Speed: Underground.
Long story short, if you think you can convert a drawing on paper into something like this
The truth is, that single picture would take several weeks if not months for one person to make, presuming they already have lots of experience in 3D modeling, texturing and lighting.