Originally Posted by
smd4
Get some compressionless cable housing and some dual pivot calipers (if you don’t already have them).
THIS
1989 frame is not going to accept, nor was it built for the forces of disc brakes. A pair of dual pivot caliper brakes with the correct reach and mount (nutted or recessed) with kool stop pads, new cables, as well as cleaning the rim braking surface will be the best, most reasonably priced, brake upgrade to a frame of that vintage.