Damn...There's some serious coin being dropped in this thread. Why not just go with a billet block and heads? I mean seriously, you've got that kind of coin, call up Bullet Cylinder Heads in Australia. Last I heard they were making a billet 2.5L block. I bet that they could do a closed deck version if theirs isn't already.
You need to hurry up and finish this project so I have some amazing reading material.