Go the Cuppa! I almost bought one of these, several times. I love driving them. They are so much fun. I looked at the idea of fitting the Hayabusa engine to one but it's crazy expensive (although the results are crazy, too!).



Capabusa in action


I also thought about fitting a G13B engine but at the end of the day a modified F6A engine (or if you can, grab the later model K6A engine. They had more torque, are cheap and later model ones even come out with VVT) would be cheaper and still produce entertaining results in such a light car. Martin Donnon bought and modified one years ago and documented it in some early issues of HPI Magazine.