I have an '02 XC300. Bought an FMF Fatty, part no. 025032. It
is supposed to fit the 03 and later bikes. I did get it to fit my 02'
Took a little pre-load persuasion, but, it fit. The forward lower mount
was a bit of a tweek, The upper rear mount since it rotates fit
better. The silencer also required some pre-load to get the holes
to align up.
It sure is nice and tight though.
I took the old FMF Gnarly from the '02 and installed in on my
'98 EC250. It fit much better with the only problem being the lower
mount. It would not even come close to fitting. The rear mount was
fine as was the fit to the silencer.
So, in my experience, it will work. Just not a sweet fit like it should.
It may promote an exhaust flange failure were it so smack the
pipe on a rock or log.
Good luck, Jeff SO. Cal.