John,
The members of this site including myself will be of more help when you tell us more about the car. The most important factor of course would be documentation. However you could have a line up of 69 Chevelles and most likely there would only be a few with docs.
The other factor will be the rust and how much there is? You`ll have to ask yourself is the car worth restoring.
Anyway goodluck and take lots of pictures. You might be surprised to find a convertable or a 300 Deluxe SS Coupe or Post Sedan.
Dan.