Its a grey area, but yeah, theoretically you shouldn't need to even have an inspection done. The job would no longer be classed as an engine conversion either, simply a modification to the original engine.
I don't know the rules of modified engines, but seeing as you can get 16v 4AGE's blue slipped straight onto the rego then I think you'd be pretty safe.
I guess I look at it all from 3 different perspectives:
1. What the RTA will pass as legit and their specific requirements
2. What police will defect you for
3. What is the legal implications of specific mods in the event that you crash
1. Its pretty easy to get most things through the RTA so long as you do a good job. Its possible to get 16v 4AGE's in legally without engineering, but its up to the inspector's pickiness. But if you did a neat job of it, most inspectors probably wouldn't even know its a different engine, they'd just write the number down and away you go.
2. Police can defect you for anything, engineered or not. If anything looks sus then they'll hit you for it. Do a clean neat job and they'll never bat an eyelid, especially if you've used the factory block too.
3. Well in most instances swapping a 4AGE in isn't going to make your car any less safe. But if you do get done driving stupidly and accidentally hit a pedestrian then be prepared to suffer.
Sorry for the long post, its just something I've spent a long time getting my head around and the system is very vague with what you can an cant do. So it will probably be useful to those who do this sorta stuff in NSW.
And one final thing I have concluded, if do so much as change anything from standard on you car and don't have it engineered then officially its illegal. In saying that, its fairly recognised that that idea is pretty anal and most institutions don't follow it.