Actually I read your post several times, but in the process of drinking several Gimlets, and kept missing the fact that you suddenly went from talking about buying/owning an '80s to a '70s favorite.
The OPs bike in the link is an Japanese built '86 Sport SX in Orchid with tange main tubes and mangalloy stays, not a bad frame. I would find it odd that a shop had one of these as a frame only unless it was stripped of the parts for some reason.
However my suggestion of just setting a price point and looking at what is available in your area still stands.
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“One morning you wake up, the girl is gone, the bikes are gone, all that's left behind is a pair of old tires and a tube of tubular glue, all squeezed out"
Sugar "Kane" Kowalczyk