They came out a while back - and I really recommend them, they sound awesome!
Im not fussed on his Shelby Daytona sounds though - they were a bit quiet at normal volume and to get the best from them you had to turn your car sound up while turning down the other cars - not the best.
Some of the sounds were good though, so I hacked some of the GT40 sounds in with the shelby ones and made a set I use for the falcon. At the high revs the GT40 goes to, it wasnt quite right just using its sounds on the falcon - even though its a 289 V8 as well.
I wish someone would do a sound set for the BMW - the default sounds are naff. I tried shifting some GTR2 sounds across, but need to do a bit of research to get them to work properly.