I got the forks and calipers but need to try find a set of cbr600rr clamps to take some measurements. I have seen a CBR400RR on the tyga website which looks to use standard 600RR clamps.

http://tyga-performance.com/site/index.php?cPath=73_869

I do know that the NSR headstock stem is longer than the nc30 and cbr400rr. Either way the best situation would be to press the nsr stem into CBR600 clamps. the top clamp has to be set down to the forktops as the the originas do or they will be too short. Even better if the 600 stem is the same length.

Here is what mr tyga said:

It wasn't a straight forward swap, so we made a custom steering shaft with a couple mods here and there to line things up. As mentioned earlier, we wanted to keep the front wheel so this took some turning of bushes and spacers to make everything line up. We then had to find a pair of rotors to match the wheel with the forks and calipers and as we had a pair of Honda NR750 ones sitting there doing nothing, they slotted in perfectly.