The Olds guys aren't as responsive or decisive as Pontiac enthusiasts, and, as usual, shipping deters a lot of potential buyers.
I've had Olds ads run for up to a month before drawing a response, but it's usually worth the wait.
You might also post, free, on
http://www.oldspower.com, which doesn't draw near the traffic of the two on which you posted, but, after all, you just need to find the one guy who has both the "wants" and the "gets".