well I got in contact with the engineering Aussie Mike recommended, and it seems that the RB26 is out of the question due to it not being a current AU spec engine.. had a chat with Scott and the other option is a 2JZ Supra, but this only came to AU as a non turbo, so I'm not sure whether this is OK yet..
750hp, Yeh, the only other 6 I could think of was the 4.0T out of the fords.. Otherwise, it looks like a V8 is my only other option, and most will know that Scott really likes the Lexus V8's..
PS: Does Scott really look like Mother Theresa?