How bout 6.7 crank with 6.7 block and some billet rods? You put a 5.9 crank in you decrease the stoke and end up with something like a 6.2l. More displacement spins turbos.
I would Put a set of Crower or woodruff Billet rods in it, and a decent camshaft and go from there with either a p-pump or an 03-04 electronics setup. Then either way you can get some RPMs. P-Pump will have more though.
Any combo you guys go, you will need cusotm rods or custom pistons. We are dealing with a different pin height between pistons. The bore is different also.