Each state has its own bullsh%t regulations but i know in NSW the officer in question cant book you for 20 km over.
As you stated there is no radar , video , etc as evidence to suggest you where and in no way shape or form the officer is qualified to
be making such claims , especially when he wasnt in his vehicle travelling behind you to go off his speedometer . Anyway he can book
you for negligent driving if he deemed you were driving in a unsafe manner . You should try fighting the fine if it means you are going to
lose your license but end of the day
the courts will see turbo skyline on the papers and the judge will try and make your life difficult. Get legal advice maybe they can help .
Sorry to hear what happened you would think the police would have something better to do then go across 4 lanes and go out their
way to pull you over . What bad criminals we are modified car owners .