Originally Posted by cannonride15

I should scan that page of the Shimano catalog, pretty sure it was first year for 600 series index. Your crankset and chainrings are also swapped from original as your Canny catalog points out 600 for both of those also, as well as the 'piece de resistance' 600 headset considered by some as the best headset ever made! I don't know about that, but mine as been trouble free since 1985 with no maintenance.
On the index mode, I picked up a bike with 105 index DT shifters with the intention of putting those on the ST400, but realizing the rear derailleur was not compatible (no screw adjuster on the cable entry) I just changed my mind, friction has never been a problem.