At the risk of being controversial, I would say that if the bike is for road use, DON'T DO IT, there's just no point !!
The bike will be much more ridable with the STD box. There is no benefit to the RRT2 unless you are racing it around a track, and don't forget that the top gear ratio of both boxes is 1 to 1 so they are the same in top gear.
If you really want it to look authentic, you could swap the internals but the RRT2 is worth at least £500 in good nick.
Apologies to those who use an RRT2 on the road.