Those cars with a 400 get bid up to around $20k at auctions, but don't sell.
The car in post #1 is a 360 2bbl slug with no performance goodies.
I'll say low bid of $8,500 and a high bid of maybe $12,500. The owner probably won't let it go for a bid in that range. However, it only takes two bidders to run the price up to a higher price. That being said, I don't see high auction selling prices in the Carolinas compared to other parts of the country.
I see nice '79 Chrysler 300 cars (factory performance goodies) NOT selling for $10k to $15k. Eventually they sell, but for how much?