This sounds very familiar.
Mine does the same.
I've got a few theories, the plenum-leak is one, and I'm investigating this further.
One thing I will say, and not be to mean, but to be supportive: Join the club.
LOTS of rams/Daks do this. So much that there must be one or two design flaws contributing to it.
On an engine that DOESN'T have the plenum-pan gasket leak, it's usually heat related.
People often use a 180 t-stat (you will lose a hair of mileage, but given your trucks size, you won't notice or care) to start with.
Also, people run lower temp plugs. I noticed that it's worse at part-throttle, which means too lean and therefore too hot inside the cylinders when then chip is running the engine in "closed-loop" mode.
So, we need to focus on keeping the cylinders as cool as we can when the chip wants to run in the most likely range to experience ping (14.7:1 Air/Fuel ratio).
My plan is to do the following:
0) check the plug-wire routing
1) Rule out the plenum pan gasket leak
2) Switch cylinders 1-4 to the next range lower plug
3) Switch cylindrs 5-8 to the next range down from that. I'll explain below
4) Do an ignition tune-up (cap/rotor/wires)
5) Switch to a 180 thermostat (Stant makes a good one)
6) Switch the coolant to 25% Ethylene Glycol A/F, and add Watter Wetter from Red Line.
7) Switch the radiator cap to a 20lb unit for a caddy, Beamer or Benz (they should all fit).
Doing all these, I should get better performance out of the engine, as it can shed sylinder heat better, and ignite the fuel when it wants to, not when the fuel wants to.
I also plan on slowly doing it one step at a time, until things stop. But I'll probably go the whole route, so that I handle the hot summers here better (100* isn't uncommon, and it's a black truck).
One of the really good articles on this problem is:
http://www.dodgeram.org/tech/gas/Trouble/ping.htm
Keep us posted, and keep it away from the dealer, if you find it's the plenum gasket, then let them deal with it if you're under warranty (it requires pulling the whole intake off the engine... Not exactly an afternoon's job).
BTW, I'm not an expert on this, but I've been doing research off and on, but it's cold/wet right now, so my truck hasn't been pinging much at all, which tends to reduce my need to get it fixed. Come summer, and lugging up the hills at 2500 rpm, it'll come back, and I'll start getting p*ssed... And then fix it for good.
But I'm investigating the wires and the plenum-pan first.