I'm going to bet that your 0331-cylinder head is has a small crack and has been leaking coolant into the engine for a while. If I remember correctly, the area in which it cracks allows coolant to reach the cam bearings. I think it's the #2 or3 cam bearing that gets wiped.
The reason you have no engine noise is because the oil pressure is bleeding out the cam bearing and not the bottom end (mains/rods).
Unfortunately, Mopar's diagnostic flow charts and schematics suck compared to GM.
But if you get yourself a pressure gauge and an adapter.... you can diagnose this.
You need to check you oil pressure @ the oil filter. You need an adapter to do this. See below. You may be able to obtain it at an autozone that lends tools.
Then you need to remove the oil pressure sensor and install the pressure gauge at the port and record it.
The oil pressure at the oil filter and at the sensor port should be within a few pounds of one another.
If the oil pressure at the filter adapter is 30-40 psi, but the pressure at the sensor port is much lower, it's due to the cam bearings being wiped. You have oil pressure down low, but low to no pressure up to.
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