Welcome mate.
QLD is definitely moving to EURO2 emissions compliance as of 1/1/08. So the old Ford 5lt is no longer a bolt in option.
It goes on completion date, so you need to comply with whatever requirements QT ask for at the time you present your Cobra for approval. So a moving bar in fact.
Best engine choices in QLD are Ford Boss 5.4lt & Holden L76 6lt.
Sounds like you know all this anyway.
Western Australia is the best state to get Cobra's registered in now. You can still use the Ford 5lt and also have working side pipes.
Have you joined the QLD club? If so, there is a fairly active northern QLD group that you should get in contact with.
I bet you can't wait to get started on your build.
Please keep us updated with your progress.