I converted my Nishiki Olympic 12 to indexed bar end shifting using Shimano 105 6sp downtube shifters (http://www.loosescrews.com/index.cgi...d=137978525403) and bar-end shifter pods (http://www.rivbike.com/products/show...-mounts/17-068) with optional Shimano spacers (part #17-135). Those shifter pods are currently out of stock at Rivendell, and I don't know where else to obtain them.

The converted downtube shifters stick out a bit farther than dedicated barcons but work just fine. They can switch from indexed to friction mode, in case--like me--you occasionally want the retro experience.

I assume you'll also need a set of downtube cable stops (such as http://www.rivbike.com/products/show...e-stops/17-045, though these are fairly widely available). My Nishiki lacked downtube shifter bosses (the shifters were clamp-on), so I needed clamp-on cable stops instead.