You get given the car when you get to B spec Lvl 35. It's stupid fast. I used it for the A spec Indy 500 and won by 40 laps. It makes a great car for faster B spec grinds, so long as the race isn't time limited, of course!
Still, there's something about that Vettel Special Event that makes me want to complete it, and I'm no Uber Completist (not even bothering with Nascar)