Started in America, with the Solstice, which is now a special color (odd to describe). Immediately checked out the engine swaps and it can use the GXP motor (2.0 Turbo) and the LS7 (Z06 V8 - 505hp). Once I get a little further where I have more money than I care about I'll put the LS7 in and super/twinturbocharge it. It'll be interesting.
I've also got a '69 Charger, '69 Camaro Z28, '68 GT-500KR, Porsche 916/4 (is that right?), V6 Clio, Wings West Civic Si, Lancia Delta, and a Border MR-2 T-bar.
I'm a little disappointed how they seem to have many of the same prize cars as Forza 1, at least at the Proving Grounds. My Solstice has been gutted (stage 2) and a better intake, which was needed to keep up with the other cars in the American races. The Delta was fast enough to easily beat the Audi S4 in the AWD races, but I had trouble using the Clio to tackle the MR events.
After intake, exhaust, and completely gutting it (-730+lbs!) I was able to get it to kill those pesky VX220s. It really took that much to barely beat their acceleration.
They did a really good job changing the sounds when you modify the car. The Solstice had a better tone with the intake, and the Clio sounded amazing with the race intake and exhaust. I can't wait to hear how some of the muscle cars sound with a freed up exhaust.