In the end, it's still no replacement for learning to render a form on paper with perspective, shading and foreshortening; all those things that take years to develop skill with. From what we can see, you're limited to a profile view, but the options for body shape creation are wide ranging enough that you can whip up some interesting forms. We're not seeing a tremendous amount of variety or originality in the screenshots at the support website sportscardesigner.com, but for $20 at Best Buy what do you want, Cinema 4D? When you're done with your masterpiece of the moment, you can export it as a .jpg, or you can spit CAD data out so that another program might be able to stitch the entire car together for you in 3-D space. It's a fun way to divert some hours, and hey, it'll keep that eternally fidgeting car-crazy pre-teen quiet for the vast span of 15 minutes, at least.
Thanks for the tip, Larry!