NADA isn't a good guide. Neither are auctions like Mecum or BJ. The best guide you can use is to go on ebay and look at the
COMPLETED SECTION for cars that sold. That'll give you a much better idea of what they're going for.
As for this car in particular, treat it like a standard 68 that's had the RS option added and an engine replacement unless you can find something proving it's a Z28.
Ed
