I've got comprehensive insurance from Just Cars for my 1jz powered ma70 Supra. It cost around $900 pa for an over 25 yr old, rating 1 driver with only 1 speeding fine ever. They do claim to have "unlimited modifications" included in the cover, as long as you inform them what they are but I've heard some people haven't been able to include all their mods (eg wheels that cost half as much as the car).
I'll be testing that "unlimited modifcation" cover shortly when the 1jz goes from twin to single turbo....
Just Cars are underwritten by AAMI so should have enough cover for you.
Still, if you are at fault due to high speed etc I'm not sure many insurers would cover your own damage.