In matters like this, my advice is to do the bare minimum, because the more you do, the more it costs.
By the books, things like seat belts with have to be replaced, however, as far as I'm aware, child restraints aren't required, as they weren't in cars in 1978.
You could go to your blue slip guy and see how you go. The worst he could do is knock you back.
Although my car is a '72 model, all I did was turn up a the blue slip examiners workshop on the day I took delivery of the car from WA. In fairness, my (LHD) car was previously registered in WA, but neither the examiner or the RTA cared. It had the rear blinkers changed to amber, but it had the original US seatbelts fitted.
Everything else is on the car is American, and it has no Australian compliance plate and has never been examined by an engineer.
I got it registered that day.