You can drive your registered LHD car anywhere in Aus. without a problem.
I don't know where you're getting your information from.
S.A. has the toughest laws regarding registration. If you want to register a LHD car in S.A. the car has to be stock, their RTA (it goes by the name of Regal or Royale or something; possibly due to the metric system, lol) won't even pass a LHD for rego if it has a modern stereo; it has to be bog stock. If you want to modify a LHD car there, big brakes, etc. you can but you also have to convert it to RHD.
If aren't going to live in S.A. you don't have to worry about registering your car there, you just drive through with your NSW or WA plates.
The latest news is that S.A. is reviewing their registration for LHD to make it more inline with the other states.
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