Few things off the top of my head... and that I have discovered recently..
1. Kips actuating arms changed somewhere around 1993 ish.. (longer)
2. Shifter shaft got larger on the splines. (1995 I believe)
3. Crank webs changed (Believe (based off parts diagrams) 88 had holes in it, 89 went to no holes..
4. head went from E1 to E2... not sure the differance... but its a differance.
5. Hmm when did they go to the final design of the kips drums? (went away from ones with holes in it)
Going to have to look that one up.. not sure if it was 88 or 89...
6. The rod changed casting numbers through the years, still same dimentions though...