Glad I wasn't around in the 70's when cops in QLD where dodgy, but doubt they would have hassled modified car owners. Mate from work used to have an old LJ Torana back in the early 90's when first got his license and when he went out in it they would see how long till he got pulled up, apparently the most times in one trip was 7, from Keppera on northside of Brisbane out to Willobank to the Drags, but that was mainly because of other things that had happened, they weren't really worried about the car.
Just get a 01/69 or older car that is pre ADR.