Loud spark knock engine running so bad the whole truck shakes

The shop that she was at before I had her towed home said they did a pressure test. They stated that the pressure was at 60 (which is where it should be they said.) Then when it then dropped to zero and would stall out. Their diagnosis was fuel pressure regulator. That was replaced but was not the issue of the knocking or running rough.

I removed the right side. No broken springs. Everything was tight. Next is to remove the left side probably in a couple of days.

I did remove the spark plug wires from each cylinder while she was running. The sound did not go away. It sounded different today though. Kind of sounds like lifter ticking.

I feel like a couple yes.

Certain ones stayed the same. Then other would cause it to almost stall. Like the second wire on the distributor on the left caused to her to stall out completely as did the third wire on the right.

I showed the video to a mechanic friend. He says its knocking from the bottom. I'm going to assume it's the rod that comes up from the bottom of the engine. Which makes me think the engine is toast.

I'm beyond curious and have already decided I cannot just stop. I'm not losing nothing by learning about an engine and in fact i'm only learning. I will take off the left side and see and then will continue doing in further.

Thank you so much for helping me. I will definitely post soon (Friday) once I get the valve cover off.

It turns out it was a bottom end rod knock. So I sold her to a guy who's going to drop in a V8 engine.