>>1449159Specifically 531, or just nice old steel? There are a lot of good old sport-tourers floating around. I think they're generally great bikes. If you can find a steel road bike, your size, with canti mounts, get it. They basically aren't any low end ones.
I have a custom 531 'ST' (super touring) frame and I really like the ride, loaded and unloaded although i've never toured on it or really weighed it down.
You might have a decent sportier sport tourer, or a 27" to convert for more clearance, that is decent, but that is more fraught. Avoid 531 Comp, even with rack mounts, as it's noodly as all hell. It's going to be a bit of a crapshoot really with a caliper braked classic road bike to see which is stiff enough for a load. Many will be outright scary but touring on an old road bike was very common and lots are designed for it. Especially fine with lighter loads and nicer roads.
I wouldn't worry too much about frame condition, especially on a bare frame. It's harder to hide (or not notice) flaws on something stripped. Hairline cracks would be issues moreso than dents. I wouldn't worry about dents in steel. Or rusting out but that's very rare and surface rust is usually a non-issue. A front end collision having bent the fork is probably the most common issue.
Mercians and Bob Jacksons are fantastic. That's a great idea. Just don't buy one of the ones with a threaded steerer. That faux-retro shit pisses me off. It's fine on a classic bike but threadless is just superior and sometimes aesthetics be damned. If you need a quill stem, they are lovely, buy an old bike.