I bought the 07 GT-R and tuned the hell out of it, got it up to 802 and it was pretty easy, also used the car for some expert tournys and it did fairly well
I bought a used Skyline GT-R V spec early in the game and maxed out the tuning,got me through the championship with no trouble (only the Team Oreca Viper popped up occasionally in the rear view each race). My reward,Blue/Blue Veyron!!
I bought a lamborghini sv, tuned it so it had 788bhp, tuned different parts until it was even more of a beast and bobs your uncle 216 mph down the mulsanne straight and corners like a house fly.
My 458 with soft racing tires and basic engine tuning for under 20.000 Cr absolutely smoked the rest of the field.
I'm pretty sure the GT-R will do an equally good job. Don't get the Murcielago.