I watched that MythBuster's episode. While they seem to do a good job testing myths, that test was performed on a small Toyota pick-up correct?
Although I fully believe their test results, I don't believe that our full-size Dodge Ram pick-ups will necessarily have the same results. You'd have to test it to know for sure.
I've also noticed that you're a big pusher on the 18* being ideal for fuel economy, I'm in the middle of an injector swap/ timing tweaks fuel economy test and 18* is one of my timing settings I'm going to test.
Have you tried 16, 17, or 19*? I've set two of my buddies mild (non-agressively driven) trucks to 18* and both claim they lost 1 to 1.5 MPG. Because of their claims, I've embarked on a larger scale test with my personal vehicle to try to find the optimum timing for my truck with two different styles of injectors.