Ok guys I work for an insurance broker in Perth. And I can pretty much tell you, when it comes to imports and modified cars you get what you pay for. Go for a cheap policy, and the wording is full of holes, not giving you the cover you need for such a car. I am 20 and have an R32 GTR, 1 accident, no claims, couple of minor speeding fines, and my insurance based on $25,000 agreed value was $3,460 with Just Car, and the excesses were through the roof, or $3,800 with Shannon's and only $1,100 excess.
RAC and HBF are fine for the little bomb that you don't really care about, but their claims services are NOT good nor are their policies. Obviously I can't afford to go comprehensive, so i'm going to go third party only. Another point worth noting is that on third party fire & theft policies, there is a value limit of $5,000. Remember that shannon's is for car enthusiasts, and yes they do ask you about this ie: competitions, licenses, training etc. Personally i'd rather pay a little bit higher premium, knowing that I am with a stable and well established company, that covers everything I want and has a great claims service. Like Shannon's.
Another one worth trying is Famous, you can call them on (08) 9388 8733 They do comprehensive cover only. And they told me for my car it would be no more than $3,000 premium. Can also try Dawes on 1800 807 463, Unique on (03) 9898 9400 or Vigil on 1300 134 054
Hope this helps. If you have any more questions, feel free to ask