Scoot-
Just got back from the Carlisle PA show, and I can say this. The 68-69 Chevelles were getting a lot of action. There is a black 68 priced at $23k with average paint that had people all over it all day.
I have had both and I would grab the 68 matching nos 4 speed car. At the very least, a wider audience, and probably an easier chance to sell if you ever have to.