the t05 turbos are a direct bolt on for Rb20, they also come with a dump pipe that joins to any aftermarket front pipe.
the 16g is good for 200-220 at 1-1.2bar
the 18g is good for 220-250 at 1-1.2bar
have used both extensively, and are a great bolt on solution. the 16g is super responsive but runs out of puff up top if you want to make much more than 220rwkw without cams etc.. I find this turbo far to responsive and prefer to use the 18g.