Ninja,
I think what most guys do to check parts swapping fitment (as far as engine componants) is to log on to kawasaki.com or one of many of the retailers who have a parts diagram and simply look-up the part#'s and cross reference them.
It would be nice to have some more 125 & 250 guys posting up,however it seems the 500 forums keep growing and the smaller bikes are hanging out somewhere else, for whatever reason.
Good Luck,
Tuck\o/