valvetrain noise 5.9 magnum

What timing chain is on there? Condition?
I'm not sure if this is what you are experiencing, but back in the early/mid 90's when these motors were new I was a Chrysler tech. I experienced quite a few complaints if excessive lifter/valve train noise in 5.2 and 5.9 Magnums. I personally never saw a cam or set of lifters go bad in a magnum back then. I tried a MP double roller timing chain in a particular noisy one, and the valve train noise went away completely. Chrysler didn't want to pay for the chain, as i recall even though it was less money in our parts dept for the Mopar double roller than the stock chain. I've been out of dealers for 17 years but i remember there being TSBs for Double rollers and or the timing tensioner from the 3.9's to address this.
These motors also had issues with distributer drive bushings. I changed a lot of those.
The third thing to look at is that it is easy to damage a magnum block if the intake bolts are overtightened when installing the intake manifold.