Popping sound in exhaust

Got a question I hope to get some direction. I've got a 360 in a Duster that has popping sounds in the exhaust. I'm sure it's not an exhaust leak; not a ticking sound. It has a deeper tone and sounds a lot like the lean out pop you might get when you suddenly close the throttle but not as loud. This is occurring at idle and also coincides with a stumble that varies in intensity. The pops are not even, sometimes happening in pairs, etc.

Let me know if you need more specific info on the engine.

Thanks.