I have to agree with the others, fitting the turbo in that location is going to be extremely tight, while trying to keep the turbo high enough to allow it to properly drain. It is an interesting idea, but if you put the turbo, bellow the rear manifold/header, the drain will end up at about the same level as where it will need to enter the oil pan, which will of-course prevent oil from draining back properly. The other main limiting factor is that by placing the turbo low, either the front or rear exhaust will be required to make a really sharp bend in order to enter the turbine; obviously not good for flow.
I wish you luck if you do indeed attempt to make this design work, but I have to agree with the others, and suggest mouning in a different location, either up front, or out back.