Charles is right..... TZ250 sometimes upgrade to Ohlins and they will be about the right set up for an NSR250.

The only issues with doing a complete front end swap from a large capacilty bike is the fork offsett and trail will probobly be wrong, not to mention too wide and likely to hit the rad or frame at full lock. This is a problem that happens with the RVF set up. (Or so I've heard).