I just had a thought this morning, I'll try mocking it up today and let you know if it looks like it will work.

03 to 08 5.7 blocks are slightly taller and the later eagle pistons are slightly shorter, I am gonna try a 6.4 crank in an early 5.7 block with the later pistons and see how far out the deck they are and if not too much then maybe double up the head gaskets as long as the top ring don't go out of the chamfer in the cylinder and skirts don't collide with counterweights...