I put a set of 2006 CBR600RR forks on my MC18. The steering stem is almost the same as the NSR one. I needed to cut the threads that hold the top bearing a little farther down the shaft. Maybe you could put a spacer in there.

Mine has the NSR front wheel on it. I made bushings to adapt the NSR axle, the CBR axle is bigger. I also made new triple clamps that are the same spacing as the NSR ones. This was part of a big project and I need to finish some other things before I ride the bike.

Peter