I will second the kaaz, i have the 2-way. I was considering the final drive swap as well but didnt do it. If its a track car then go for it, you will get the most out of the full set of gears. Otherwise 6th is redundant. If its a daily/commuter car best keeping final drive to keep revs and fuel use down in motorway.
I have a spare std diff and housing if you want to build it off the car.