Ive done the conversion on my n/a, i simple bought the full engine with turbos,loom and ecu's from a slightly smashed up supra.
It really is a simple conversion im a builder and i did it with a mate over a couple of weeks. I paid £1400 for full engine, About £550 for full exhaust and decats, £300 for intercooler. While engine was out of car fitted new clutch, water pump, cambelt and most other things but only because it was easy to do so at the time.
You also need the rev counter dials from a tt as the n/a dials wont work, also a bigger fuel pump is better but dont have to.
Im also using the 5 speed gearbox that everyone says will brake but mine is still fine and been using it for over a year now. Im upgrading my twins after christmas so they will run 450-500bhp just to see how much the 5 speed can take. lol.