Also interesting is the approach taken. I would guess most Europeans would opt for a very economical Diesel car with excellent performance instead. E.g. a MB E 250 CDI, top speed 240 km/h (150 mph), but uses 5l/100km of diesel fuel average (47 mpg), perhaps twice that at top speed (23.5 mpg). With the standard 59l tank that would give it a range of at least 590 km as a standard car (when driven at more normal speeds, a range of almost 1000 km's is possible).
After all, on a race this long, it is the average speed that makes the difference, not the acceleration to that top speed (although the E250CDI is no slouch at 7.7s to 100km/h), and the amount of time not driving at that speed.
On a trip last year to our skiing destination a friend in his V8 Supercharged Range Rover and I in my puny 2.5 liter diesel Touareg left at the same time, drove the same route through Germany, in one day. We left very early (at 5 in the morning) to avoid most traffic. Needless to say, when we entered Germany he sped off in a cloud and left me virtually standing. I arrived, some 1250 km's later almost an hour earlier than he did. I needed to get fuel once, and he 2x. The second fuelling delay got him into more traffic around Geneva and he was toast. (Note: Speeding in Switzerland is not advised and we did not).
On the Cannonball run I would probably aim to optimize my route and take-off time in such a way that I'd hit the higher traffic density areas at times when traffic is light and optimize for that.
As Flyair said, here in the Netherlands we have these "average speed camera controls" over a number of sections on our motorways. They are very effective, because you see everyone slowing down to this speed. However, this is in a very busy area. If you are "breaking the law" for a record attempt anyway, why not go the whole hog and steal someone else's number plates? The point is with camera controls, they don't actually attempt to stop you…
Peter