Hello sir,
I own and still using the 1999 KHS Comp ST with orange color and 19 inch size frame. I dont know the exact axle to crown length the manitou spyder R which OEM with the frame but i know the frame is build for 80mm-100mm travel of fork. My bike is using the Rock Shox Judy (yellow) 100mm as replacement for the Manitou since the elastomer inside the manitou is melting due the time.
If u planning to equip the frame with above 100mm travel of fork, then u need to compensate the slower turning maneuver cos the front angle design of the frame is to accommodate 80mm-100mm travel of fork. I've been using the Rock Shock Pyslo 125mm to the frame and the result is not satisfied me, so i return to Judy 100mm for sharpen turning and moderate bump eater.
Great frame design of soft tail, it does have "soul" in it each time i ride on it. I love it very much and couldn't find any match experience with other frame including full suspension.
Cheers.
ps. do take your time when dismantling the rear shock, the rust might built up inside it especially the inner bolt.