I personally would LOVE to find a rebuildable '81 PE-175!!
If there's anyone in the Michigan area that has one, PLEASE PM me and let's talk!
As far as you picking one up, consider this (IMHO):
Never buy a vintage bike just because the asking price is low. Rebuilding a vintage bike in most cases can end up costing more than a modern bike, assuming that your even able to find all the parts. Manuals and techinical help is mostly lacking on older bikes too, so you kind of need to know what your doing before you open your wallet.
Only buy or recondition a vintage bike if you've always wanted one of them, or emotionally tied to it in some way ~ ie. it's my dad's old bike, or, this is the bike that I wanted back when I was 17!
There's more good reasons, but don't do it because it has a cheap "buy it now" price tag. You'll be shocked when it comes time to buy parts that no longer exsist...