I actually like the look of the looping cables, but that's just me of course. I think the looping cables, along with the old treaded headsets and quill stems made the bikes look more graceful than the modern threadless headsets and stems.
Depends on the vintage parts, I found just 2 months ago a brand new in-the-box Suntour Winner Pro freewheel from the 80s, and they're were a lot of them, for right around $50. I would have thought that gears would be very difficult to find since they are a wear out item. Keep in mind too that the older vintage stuff lasts a lot longer than the modern stuff does, I have a bike I bought in 1984 that has Suntour Superbe groupset on it, and it has over 150,000 miles, and about 1/2 of that was racing or training miles, and all the miles were riding in mountains, and they still work fine today! I heard from others that groups from any manufacturer made in the late 70s to the late 80s were capable of doing those sorts of miles.