Having the engine built here in Oz is not a stupid idea. I am able to source all the parts for you (as could many other people) and then get a reputable engine builder to build it. I would start with
THIS block. Its a Dart aluminium block with 84.5mm bores and steel main caps. You also have the option of the B20 block. The most important aspect of that particular block is it is a closed deck design.
My one big problem with what you want to do is your budget. For that power your budget may take a bit of a hammering.