Wow, Larry! I'm surprised we haven't already created such a list in the MX Library. (Maybe after everyone logs on and helps out with this question I can post one there.)
Things to look for when shopping:
1. Complete logs which include 337's for damage repairs.
2. Corrosion. At wing attach blocks, at horizontal attach, at spars and carry-through. Doorposts , firewall, and gear bulkheads clean and without wrinkles, damage, etc..
3. Rudder cables within rear bulkhead (a blind spot) including at fairleads. All the rest of the flight control cables, including the flap cables from the flap handle up/out. Check the flap lever pawl rivet, per the caution in the MX Library.
http://cessna170.org/phpBB2/viewtopic.php?t=2231
4. Tailwheel steering cross-over pulley attach/security in 55 and later models.
5. Aftermarket mod documentation and approvals. (This is a tricky one. There are so many available mods that at first glance might not be evident, such as vacuum pump installations, engine/prop combinations, gear leg change-outs, wheels/brakes other than original Goodyear, instruments/panel changes, "single-piece" windshields, different yokes/handles, alternator conversions, wings from different models installed, tail-pull handles, cowl-steps, fiberglass fairings, vortex generators, etc. They each and every one must have a basis of approval and a form 337 referencing either an STC or with "block 3" approved by the FAA.
6. Non-aviation equipment installed without approval (auto stereos, etc.)
7. Annual Inspection items, (an annual should be performed for YOU as your pre-buy inspection when you are virtually settled on a particular plane, and the title check is clear.)
This will catch most items, as long as you don't accept the current owner's annual inspection as yours, and the inspection is not performed by the last couple of guys who did them.