As for my experience all 41mm from NC23/NC39 and NC27 I think too. NC30 is too short. And one more - if you going to fit original calipers only this forks fit.

BTW, if you decided to change forks, I think better to take full front end from CBR900/CBR600RR. Both possible to fit.

CBR600RR
http://img.moto.kiev.ua/thumbcache/7069 ... 683344.JPG

CBR900RR
http://img.moto.kiev.ua/thumbcache/7519 ... 945558.JPG