Sure, it's a 6, but it seems pretty affordable considering it's being offered by a dealer (which immediately sends a red flag, but I can't spot anything obviously amiss with this one). Looks decent and seems to have its original interior. If you could get it under $20k I think you wouldn't get hurt...and since a dealer is offering it, I'm guessing there is some room in the price....
Link to 1968 Camaro Convertible auction