hello...
the cases will fit from 92-2004 to the transmission, but there some little differences. the kx250 92 to 96 cases are the same,
in 97 kawasaki took some little changes . another shift forks with bigger pins .which means you could in 92 case only use shift forks and pins 92-96 and in the 2001 case only the forks and pins 97-2004
in the 97 to 2004 cases is a bolt-less on the clutch cover, which means for example that the 2001 clutch cover not fit to 92 cases...
the kx250 transmission gears and shafts are the same 92- 2004 . since 99 is a finer toothing for the sprocket on the transmission output shaft.