Dylan - in Qld, if a motor is changed to anything different to what was originally put in there, we need a Modification Plate fitted which is the same as your Engineers cert. I copped a defect ($250 fine) for not having it so I'm a little puzzled as to why NSW wouldn't worry about something like that when they are so strict on other bits and pieces. Who did your blue slip inspection. Did you make them aware that it was a totally different motor completely (ie: out of the twin turbo model) or just a new motor (motor blew up; just replacing it with another one from the wreckers yo)? I'd suggest having a chat to a few different places down there that do blue slips/ roadworthy's/ safety certificates and tell them the full story about what you've done. Not having a go at you mate, just don't want to see you fork out money for something that could have been prevented.
BTW, aren't you supposed to be coming up here sometime soon??????
Haha not sure mate, money is a bit tight at the moment.
Yes, I got my blue slip done because my vehicle was not registered (rego expired during conversion). So not only was a blue slip needed for the engine SWAP, it was needed to get the car registered again too. The RTA registered the vehicle has having a 2.0L Turbocharged engine (its single turbo mate

) and so did the blue slip place. What I've done is legit and no corners have been cut. The RTA REQUIRE you to do everything correct, which I did and the vehicle is road registered.
I believe I need an engineers certificate for my exhaust, however the engine alone does not require one as the X-member was the same and the engine has been swapped and correctly registered through the RTA.
Dylan