The Bianchi Special by Columbus decals indicate a 1985, Italian manufactured model. It has been frankenbiked to an extant that that the exact model is indeterminant but the presence of a chromed, drive side, chain stay suggests a Mondiale or Campione. This assumes it is a USA market model.

Regarding indexing, I'd probably go with 7 speed Shimano, unless you're prepared to cold set the frame and invest in new wheels.