When fabricating a set-up like this, the headers are the last thing you build. Place your turbos where you want them, do the accessories the way you want. AC, alternator, etc....Then build the tubing to connect the dots.
Using someones else's idea of where stuff will go will set you up for some miserable headaches. And that's exactly what pre-made headers will do. They don't even get you half way there. Everyone's set-up is different. There's too many variables.
Been there.