NSW. A few years back I engineered my GQ with 6" lift & 35's. Engineer said it would be a good idea to engineer the turbo setup aswel as GQ TD42 never came from factory with a turbo. Cost me an xtra $100 but same deal, had to fit a muffler to quieten it down.
I think you will find that you will get different info from different engineers/certifiers as from what I can work out it's a bit of a grey area. My 2 local engineers wouldn't engineer a Patrol over 3" lift with 35's. I know they both work together & they are bios! He passed a landy with 35's & a jeep with 37's so I searched further a field & found quite a few who would engineer it but price was way over the top. then I found my current engineer, strict but good on price. Didn't bother me as I wanted it 100% legal for insurance purposes & safety.