Sounds like timing chain issue to me. One (or more) of the chain guides (together with gear and chain, "cassettes") has failed--meaning broken/disintegrated. When this happens, the chain slaps around (can be louder at lower rpm) and chunks of the guide are strewn around the engine, potentially blocking oil passages. Especially common is obstruction of the oil sump in the oil pan. 180k miles is a normal time for this to happen (4.0 SOHV engine). Mine happened @ 179k.
Good news: Your chain has not slipped (yet) and done serious damage to your heads (esp. valves) and pistons.
Recommend that you STOP DRIVING THE CAR immediately. If you don't, a timing chain WILL slip and you will bend valves and do hundreds of dollars more damage to the engine (mostly heads, but potentially the block/pistons as well). And since your oil pressure maybe compromised at points (oil pressure gauge not a reliable indicator in this circumstance), you could do serious damage to the lower end (bearings, etc) as well.
One relatively easy (emphasis on "relatively") way to verify is to drop the oil pan and look for chunks of amber/orange chain guide. Be sure to look for chunks wedged into the screen in the oil sump. You can all pull the valve covers, but that's not easy.
Next, you may want to do a compression check of all cylinders. This will give you a good idea of the health of the cylinders (piston rings) and heads (valves). If the compression looks good, and you like the truck and its in good shape, its probably worth repairing the engine/timing chains. Lots of good info here (esp. StreetRods's posts in the 2nd Gen forum; same engine).
Next critical point is to figure out WHICH guide(s) has(have) failed. As you may know, there are two timing chains (three, if you have balance shaft engine) on the front of the engine, and one on the back. Could not tell which one failed from your video. There's a big difference between a front secondary (driver side upper timing chain) failure and a rear (passenger side) failure: you have to pull the engine (or the transmission) to do the rear chain, but not to do the front. I don't recall whether you need to pull the engine to do the front primary guides, but I don't think so. StreetRod would know.
If its the rear chain, you'll need to pull the engine--a big job. The upside to pulling the engine is you can do a lot of overhaul easier with the engine out. You could even replace the head gaskets, though they are not known commonly to fail on these engines. (I would only recommend if you had some coolant loss; ever overheated the engine; or were concerned that a prior owner may have overheated the engine. Or if you like the truck and want to have a machine shop overhaul the heads for better compression, longer life expectancy.)
I recommend Cloyes timing kits (OEM). They have a good video on replacing the cassettes and re-timing the engine. Its tricky. You need a special $200 tool (OTC), though some brave souls have chosen to do the job w/o the tool
Depending on how far you go and how many other parts you decide to replace along the way (radiator? harmonic balancer? water pump? thermostat/housing? sensors? plugs? wires? belts? pulleys? Head bolts? Gaskets (yes)? Starter? Etc., etc.) will likely cost $500 (bare bones) to $1,500 in parts.
Hope this helps.
