I hear ya'...after I posted my reply up there, I looked to see what the 5.2 requires in my books, and there's not much in the way of options for your engine.
Something did occur to me though, you mentioned the plugs had reddish deposits on it. That's not overheating, that's fuel additive deposits. If your air/fuel mixture was too lean, causing an overheating problem (and/or too high of a heat range), your plug would have some different indicators than you mentioned.
Overheated plugs would have kind of chalky looking insulators, pitted electrodes and a dark blue (real dark, might even look black) shell. I have even seen blistered and partially melted electrodes, with what looks like metallic splatter on the insulator. This can be caused by bad timing, bad EGR, a vacuum leak and like I mentioned above, bad air/fuel mixture or too high of a heat range on the plugs (or a combo of one or more of these).
Whatever you're putting in your fuel is the culprit there, mister...otherwise, I think you're ok...if you have a good engine tech back there in your neck of the woods, talk to 'em about what I've mentioned and see if they agree.