Race cars are definately in, if it is a truck, car, motorcycle, or motorized unicycle available to the public (even if only members of the public with very deep pockets) it would qualify. they do not have to be street legal or in regular production.
By general automotive I mean wide open, to generally civilian ground transpotation, not refering to only "regular" cars you see on the street. Somewhat Sci-fi cars like Speed Racer's Mach 1 or the Batmobile, and even bizarre stuff like some of the Wierdoes models (those with a ground vehicle anyway) would also be acceptable if someone wanted to go that way.
If you would post the finished model in the automotive section of the forum, it should be fine.
Also started models will be allowed as long as you actually have a fair amount of work to do before it is finished. If it will allow a few weeks of participation in the GB I'll allow it, if it is going to a post with here is what I'm working on, followed an hour later with a here is all done now that I've glued the bumpers on post, then it isn't. A certain amount of the honor system will be in effect when it comes to started kits.