The problem with routing the turbo into the engine bay is still, in fact, space. I agree that there is enough room where the battery used to be for the turbo. How exactly would the routing go? That transmission really limits you in space. If you're coming back into the engine bay you have to run the exhaust from the rear bank back up to the front and then run a bigger exhaust yet back to the rear again. Thats not even if you want to intercool it which admittedly probably would not be that hard. There is plenty of space there, but I don't know where you would be limited there. Rear mounted turbos may not be as efficient as the other option, but they have been proven and for only 500 horsepower I believe is the better option not only because of room but the extra piping acts as an intercooler itself. My vote goes to rear mount. You just need to figure out the right size piping to run back to the intercooler and then back to your intake.