Might it be as simple as requiring scale sized (diameter, anyway) wheels? In my memory, the only really odd thing about the out and out race cars of the 68 onward period was those tiny wheels, front and back. Especially on open wheeled models. I have nothing at all against vacforms per se. There's such a range of models you can choose, and they're great for racing; cheap too. You can make them look as good as you like. I don't think the problem lies there, particularly. Whatever anyone else has to suggest, I think it well worth pursuing the idea of scale racing!