Long time no post - 1998-2002 GTX is 'roughly' the same hull.
my 2002 GTX rode smoother and tracked straiter than my 1999 GTX LTD however, so it may not be exact.
Engine size however would determine things like engine mounts, exhaust location, etc. that cannot be easily changed.
1998 had 3 gauge cluster. 1999+ went to two. the remaining changes were mostly cosmetic. 99+ uses a plastic pump.
Man, I really did know this stuff lol. Also 2001+ used a different rubber flap on the air intake of the 951.
I could probably list a dozen other things too between 98 and 02 that changed, but they shouldn't affect much. unless you want to get into dual ignition coils/wasted spark design/etc.
I do miss my skis lol. but if it's 80 and sunny, I'll be on the boat