Why single turbo? Has anyone even done this? I'm not sure there is room to do what you are trying to do.
I'm not too up on my knowledge, but aren't there bolt on upgraded turbo kit's that will make a lot of power... 600-700whp, maybe more?
What are you trying to accomplish? What are you trying to accomplish that can't be done with existing parts, which will very likely be easier and probably less expensive in the long run?
You're a shop owner, but your shop can't do this?
Why not use the stock manifolds, or many of the aftermarket ones that are already out there, and just go from there?