To the best of my meager knowledge the subframe from 94-98 KX 250 will bolt up to, at the very least 01-06 GG. Even as a complete unit, including the airbox, and boot to the carb. If I ever get back on track, my 01 XC will have a complete KX tail section, borrowed from a 95.
the 94-98 KX250 suframe is a definite bolt-on, for your bike. Even the GG & KX air filters & baskets will cross over each other...regardless of part numbers. I haven't tried fitting to any 02-later Gassers, but my 01 XC sits on a 95 KX rear wheel...FYI