Spec Racing

F40 vs F50

XJ220 vs EB110SS

McLaren F1 vs Veyron

etc

An Agile Llama wrote:

McLaren F1 vs Veyron

That wouldn't even be a race. The Veyron would decimate the F1 off the line, and then fail in the corners. xD On a straight line, the Veyron would win, but not much else.

The F430 is notorious for it's understeer, I've never been happy with it in S class, especially since there's the 430S which is a much better car. The best luck I've had with it is keeping it in A. Race tire compound, increase 1 size in width, race diff., sport supension and full roll cage. (I believe that keeps it at A600.) This is the best use I've found for it, it's not the strongest, but it's better than it was.
For the Ferrari/Porsche/Viper/Vette race, the cars are going to get very few upgrades - race diff., race compound and some will get tire size increases, the PI's will generally be around 610-615.