Not quiet Dimis but nice try
The theory is that the engine needs to be suitable to adhere to the ADR requirement for each individual state, so for S.A. it is still ADR 37.01 and for Vic and NSW it is Euro 2+ emissions requirements. What this means is that the level of Carbon monoxide and hydrocarbons produced needs to be below the mandated thresholds for an engine running in an ICV.
In S.A. that is 2.5 percent Carbon Monoxide and 250 parts per million Hydrocarbons.
In the other states Euro 2 specs are slightly lower than these figures and engines such as windsors, VN 5Ltr engines etc.. do not meet the requirements and are therefore deemed to be unacceptable for use. That said you can still put one of these engines in an ICV but it will have to undergo an IM240 engine cycle test, whereby they put the car on rollers (in an enclosed room to suck the gases out the engine pipe) and run the engine through it's rev range under specific loads in order to capture the gas emissions produce, and it's a pass/fail thing at a cost of over $1000 a throw in certain states.. The acceptance for individual engine families is generally based on the year of the car and the ADR for each individual state, so anything preceding 2002 in a Windsor based engine will comply as long as it is stock standard and runs the original ECU, loom etc.. etc.. I would suggest that a LS7 engine would come out of a car post 2002, therefore it is OK to use within S.A.
It does get quiet complicated in Vic and NSW as the EPA in their infinite wisdom have up'd the ante and made it harder for guys to comply ICV's primarily based on emissions targets, that's why a lot of guys are now looking to the Coyote motors and LSA motors.
The other thing to take into account is that once you have chosen a builder for you Replica car then immediately get your statement of requirements so that you are locked in to a given compliance criteria whereby even if you take up to ten years to build your car, the law is not retrospective and the transport authority can not make you upgrade your engine spec. Just as long as you renew the S.O.R. annually - some people wait until they are finished building before they get their S.O.R. and get a nasty shock when their engine is no longer valid.
Hope this long winded detail helps.
Cheers