thanks for the reply. Most of the cars I've looked at usually have had more than one pervious owners and don't have all the records. that's why I wanted to find out if there are any visual signs I could perhaps look for to spot out if the A/C system has been worked at and the more expensive parts, for which I've read the labor/parts could end up in the $3000 range, have been changed already.
As for waiting for the car with all the records, well.. I've usually seen those cars advertised for way more than the market value. sometimes 5K more. I'll take the records if the owner has them available, but i'm not making it a point to wait for one that has them all..