Fitting early model RS250 carbs to an NSR is relatively easy. The key is the manifolds. The early model RS250 manifolds (90 deg) are no longer available from Honda. They only show up whn someone is parting out a bike. If they are going on an MC 18, you just need to get rid of the oil injector. If you wanna put them on an MC21 or 28 then you need to fiddle with the TPS. Finding a set with manifolds and the throttle and cables is a huge plus. As far as setup, its up to you. If you don't have alot of experience jetting a 2-stroke or a racebike, I'd stay away from these. If your no intimidated, its a nice mod that can yield some nice high RPM power.
Chuck