Just re-read the OP, and for the S-Class events, you may want to consider the Light Car Company Rocket. It's a prize car (not sure what for at the moment) or, only costs 100,000 credits, and can be tuned to 650 pp. It may not be the out-right fastest, but with only a four cylinder engine (only weighs 390kg) powering an open-wheeled body, you'll have an enormous advantage in making far less pit stops (if any) compared to the AI, due to it's incredible fuel economy.
Sorry for the double post, mods.