Must talk to your SA rego people - it is often posted how strict they are with originality.
Apparently SA rego is much stricter on any modifications than DOTARS, the import licence people in Canberra.
You need to buy a car, then apply with the details for an import licence before shipping. It's been said there's about 2 month's delay with this, so consider how you will store your car in the USA.
Talk to a local Customs Agent before you go to get an idea of landing costs, and of course GST. Luxury Tax applies if it's a high value model.
