So, what you are saying... is that you want to build a rotary powered locost?
Well, that's not easy, but it is certainly not hard either, and others have done it with a varying degree of custom fabrication. When you say "car", what "type" of car are you looking to build? I think something like a locost seems to fit what you want to do.
It's a spartan, do it yourself ride that can get great gas milage, low maintenace costs, and that also happens to be a good bare bones sprots car at the same time.
Also, I like the fact that you use proper grammar, and your writing seems to be top notch, but you can just use conversational language on forums, so dont sweat it!
