The Magnum trucks will often "feel" different based on the calibration it's running in factory truck applications. Check the PCM and around the engine compartment on the 5.2 Magnum trucks, looking for a campaign label saying a dealer recalibrated it at some point. If the label is present, you likely have the Magnum "death flash" that takes away a fair amount of power and fuel economy because they were compensating for some of the common issues. If so, an aftermarket tune will level the playing the field quite a bit. A good 5.2 Magnum without the death flash will often feel much closer to a 5.9.
I am assuming original post was about a carbureted engine. And if it were me and I was sure it was an internal noise, I would tear down and inspect it. As others stated, if the bores are still good shape, most everything else can be fixed fairly cheap.