The rear derailleur and seat are obvious replacements. It may also have upgraded to 7 speed. I don't recall these coming stock with an internal computer hook-up but that sounds like what it is. Continental are very good tires at their respective price points.

The ST (road version) that I recall typically was red with gold decals and chromed fork crown and dropout flats. If this matches yours then original price was $350 US and the age is a bit older than 1987, about 1984. Tubing is good quality, butted Ishiwata CrMO. They were nicely made, though nothing special. Provided it fits and is in good condidtion, it's good deal.