Anyway you need two sets of NSR carbs, I used MC21, and 1 set of NS carbs to use the brackets etc.
The biggest problem is you have to bore out the NS carb to reed rubbers to allow the NSR carbs to fit. I got a company in Reading to do it for me, cost about £40.
The choke is different, the throttle drum off the NS400 also has to be used, and on mine I had to file it down in one place (or a bracket or something) to get it to open to full throttle. Somewhere on the NS400 forum there is a post about it.
I have no airbox, will have ramair filters due to space constraints, and I went for 192 jets in the front, and 195 in the rear - this wasn't done scientifically - just a guess to give me a safe starting point. I've not ridden it yet.
Hope this helps...
Cheers, Mat.