Good luck with the MC18 build. Although it's not quite so easy to work on as the MC21 and MC28 (a little more room in the frame, and better laid out), I think you will be amazed at the difference between it and the VJ21! It's in a whole different league to anything else of it's era.
You don't say which model it is. Is it an R2/4J (Mk1/SP) or R5/6K (Mk2/SP)?
In answer to your forks question:

RVF400 NC35 forks on an R5K. There are drawbacks though. Reduced steering lock, being just one of them. I'd be more inclined to go for MC21SE forks, or the NC30 conversion if you want bigger discs, but in reality, the NSR doesn't need them. If you go for MC28SE forks (or SP if your budget allows), you can use the later Nissin calipers, which some argue are better, but I can't see it personally. I think those who make the claim just like the fact they can get gold calipers from a different model, and are simply "parts tarts"!

_________________
Andy.
NSR-WORLD.COM
Please keep all responses to Forum posts on the Forum so that others may benefit.
Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
Check us out on Facebook! Please "like" our page!