No SR20DE's came from factory turbocharged. Thats why Nissan left the T off the end of SR20DE.
Nick what your friend has said sounds like a good idea. I would dump it infront of the diff. Since you plan to run nitrous, you want very little backpressure so you can get rid of all the spent gasses quickly - just like on a turbo setup.
The idea of your friend to also make the exhuast easily run a full system sounds perfect. That way when you arent using nitrous, the ute will still have good bottom end power for driving around town.