I get asked this question on a daily basis.
It can be done in any state, it just finding the engineer that knows what they are doing. All states follow the same ADR rules, so state to state makes no difference. If you just roll up to the Motor reg. department and ask they will say NO, that because they are going by the documents from the guidelines to modifying a Vehicle. These are a Guideline not the rule book. If you engineer can prove with evidence that you car out performs all the required ADR's they can not so no. We have been doing this for years in Adelaide with a few different very good engineers. Its not cheap, so dont think you can get it done for $500 or $1000, they normally charge $2500 upwards, depending on what you are doing. My engineer has said to me, that using a lot of my products and my fabrication, we can get a twin turbo LS regoed. And before you say it (my states rego department is the hardest to deal with) not true. It finding the engineer is the hard thing.