Resale value? 69 Convertible will be your best bet out of those choices. Followed by the 69 coupe.
67-68 Camaros generally don't pull down the resale that the ever-popular 69 does. Firebirds typically have a worse resale than Camaros.
This is of course, assuming that none of those cars is a limited production model, etc..
If you want to build something different however, I'd go with a 68 Firebird. A well built LS1 1st gen Firebird will attract alot of attention since there aren't many out there.