The model might be fairly easy to bring over but the physics will have to be written from scratch for AC.
Not really, and not allowed. Tires yes, Kunos has added those "in bulk" to the SDK folder. But suspension wise you are better of starting from scratch, especially with those old Australian muscle cars. AC physics are based on geometry.Probably easier to modify an existing car by putting the body on it and just altering the physics huh?