Just be careful of component prices if building from the frame up, particularly with sought after vintage parts. Modern group-sets shift so accurately and consistently, even those in the lower echelons.
I've got a 1987 105 group-set with down-tube shifters which work on indexing or friction, combined with a uni-glide cassette. I've owned it since '93 and the bike's been pampered. It shifts extremely well but it's not a patch on the Sora group-set on my Allez with HG cassette from 20 years later, I wouldn't expect it to be. The UG cassette is close ratio and replacements are rare and expensive (when I've looked anyway), although they do seem to last longer and the cogs can be flipped to double their service life (except the first which acts as a lock-ring.)
To some on here '87 is barely vintage. If you know what your looking for and are aware of the rear OLD/frame spacing anomalies then you could end up with a great bike. It would be interesting to see which you prefer, that or your
Ribble