Speedo conversion. Which will fit an nc21?

[andy1472]

Hi. I'm looking at converting my km clock to a mph clock. I do not want to fit one of those converter gear gagetts or use overlay stickers as they look a mess and can be at least 10mph out.
I'm forever either going to fast or usually too slow.

I know some models have interchangable parts. For instance I have a front brake master cyclinder and lever straight off a cbr600 with lever adjuster and it went straight on. It's a superb alternative.

I need to know if someone has done it and it works rather than "i heard this fits".

Thanks for any help people.