One of the main things will be selecting the right turbo. You can turn the boost up, but your turbo will need to be rated at about 600hp. (Your motor will be making near 600hp to get 300rwkw.) You can go to the website http://www.turbobygarrett.com/ and have a look at a few, and read the tutorial there on selecting turbos. The plain bush ones will be cheaper, the ball bearing ones will have less lag. Both will make good power.
Then you need to do some simple maths to see if the injectors are up to it...
A programable computer is needed. The Nissan computer can be played with and reprogramed. Or a stand alone afermarked computer can be used.
Appart from obvious things like exhaust and intercooler size, the car needs to be started and tuned by a expert. It can be tuned on the road with the right gear, a dyno is not needed. Unless you want a printout showing the 300kw.