Why not the touring bikes, as that is what those vintage tourers were made for? I am not up to that level, but did it years ago and if I were to progress to that level, my newly acquired miyata 1000 would be my choice over my sport touring bike that is a wee bit lighter.
I guess the added comfort and stability would lessen the fatigue factor greatly for mere mortals. The vintage tourers it seems are way more sport leaning than the dedicated tourers of late.