[WSSix]

If your noise is the same as the GTO, then it's the engine. I'm almost 100% that was an engine problem in that video. I say almost because I'm human and not perfect. If it were my car, I'd be going into the heads inspecting the valve train and springs. It's so simple to pull rocker arms and check springs on these engines. There is no valve lash adjustment. You just screw the bolts down and torque them.

If you're going to pull springs to inspect them, I prefer compressed air in each cylinder to hold the valves up. 30-40 psi does fine. You can use a simple lever action compressor or spend the money on a double compressor from Crane Cams.