i havnt done it but at a guess if you use all factory parts then nothing as VLs also came with a turbo RB30. upgrade brakes to turbo items and polution gear too. that is all i can think of.
didn't think you needed to pass engineers if the model of car come out with that engine from factory?
only think you will need to worry about is more then likely, emission laws.
but ACT could be different from VIC.
Yea well it's not quite standard , bigger turbo on stock manifold with external gate , cooler , ect... But if I but disk on back and twin piston on the front it should be right yea?