Originally Posted by
fietsbob
If the front end of the frame was made for a short blade Rigid fork,
raising the frame to make room for the travel of a suspension fork,
changes the head tube angle ,lower than the frame was designed to be
so will change the handling in an unpredictable way.
+1. I tried an aftermarket shock on a 1992 like that, and reverted to rigid. While the shock made bumps less jarring, it also wrecked the handling so that I could not avoid rocks, roots, and other obstacles. If you don't want a rigid ride, sell this to a C&V enthusiast !