I really don't see the need to go with so much displacement that you have to use an aftermarket block. Why do that and have the extra expense when the goal is 550-600 hp in a streetable package? A 489-496 CID based on a production 454 block with good internals (same quality as inside a 502 or 540) will cover all of your needs and still offer room for more power down the road. (try getting all of that torque to stick to the road, not easy. More power will just be wasted)
If you use 489 inches as a starting point, add a good hyd roller cam, decent heads, good induction and exhaust and keep the comp ratio at a reasonable level you will have a 600+hp motor that runs on pump gas and will last you forever. More cubic inches is great at the show when the other guy asks but it will serve no purpose in THIS application. All it will do is make the overall cost of the build higher. Unless someone has a line on cheap 502/540 size blocks?
Of course, I could have my head way up my a** here. I still say go talk to Mike and tell him your goals.
Just my .02