I have a 1988 Miyata 312 with all original components. The rear derailleur, a Shimano RD-A350 with 6-speed SIS index shifting is broken, and needs replacement. Sheldon Brown says that almost any post 1997 Shimano RD should index properly.

http://www.sheldonbrown.com/dura-ace.html#indexing

It would be comforting to get some verification of this.

While I would prefer to retain period correct parts I would not be too averse to using a modern Shimano derailleur such as a Tiagra.

What are some suggested options?