[boxhead]

Dazza, your proposal of seeking approval to build before comencing (to lock in ADR's) is exactly how it is done in the NT, Before commencing you fill out paperwork for "Approval in principal" on this form you supply all info regarding the build and forward it to the MVR(Motor Vehicle Registry), they sit at the start of every month and will either approve (and supply a build number) or advise what corrections need to be made.
You then have 4 years to complete your build, if you do nt finish in time you can apply for a 2 year extension.
I personally know there is a Roaring Fourties GT40 in Alice being built (the build has been on for a large number of years) and his emissions allow him to run webers.
I personally was also exempt and permitted to run live side pipes, chrome dials, alloy steering wheel and no crash pad, as the vehicle was being built to replicate a car that had these items (I did still need to run cats and heat shields).

If you want more info on the NT system, let me know.