I've also had similar experience, the 5.9/360 in my Duster has ported Edelbrocks and 9:1 compression while the 360 in my D200 has stock iron heads and 8:1 compression (rated 8.2:1 but likely lower). I've never had the Duster engine ping even when the ignition timing was overly advanced but the truck engine pings like a SOB especially in hot weather if it has just a little bit too much advance.
To add to the OP's original question, I've had issues with an early 340 driver side manifold interfering with a factory Magnum head in that same location as the Edelbrocks.
