NSW you'll likely need to go through the standard engineering process.
You'll need to speak to your engineer of choice who will tell you what they want done to the car for them to certify it, then on top of that you'll likely need to book in somewhere to do a brake and suspension test etc.
Then once thats done, you take all that paperwork to the NSW RTA and submit it.
Not sure in NSW, but I know in SA it's about a $10k and 3-6 month excersize for an LS swap into a 2nd gen to make it totally legal. But thats because they rent out a race track or an air strip etc for the morning to do the road test portions of the engineering, it may be different interstate and able to be done on a dyno or something.
But yeah it's not as simple as everyone thinks where you just speak to an engineer, do what he wants and then get it passed.
TLDR: Find an engineer and speak to them, every engineers going to have a different set of criteria they are going to want you to meet before certifying.
Engineering in Australia is brutal in general. And the big thing to remember as to why you want it engineered is more for insurance than being rego/street legal. Even if it's registered as a V8 currently, if it's not engineered with the engine thats in it, and you crash it......your insurance claim won't get paid out, even if you've declared to your insurance company it's LS powered.