'67 Barracuda Fastback S 383 4 speed rear end issue?

Now that you mention it, it may be happening more on turns, but I would swear it has also happened on a straight away. I will pay more attention going forward and try what you suggested. I looked at the clutch pedal and could not see anything that looks like a spring on the mechanism.
Well, I would definitely crawl under there sooner than later or have the previous owner informed of your concerns before some nightmare ruins the car and your day. That can only get worse.