Jerry, I don't know personally why an AD truck would need to be lowered 3" or at all. I was repeating what my neighbor has told me several times. My thought is that is his opinion because of the hot rods he builds and he is a perfectionist for optimal handling.
I would like to retain as close to stock ride height as possible so I can put LT tires on it and it will look like a truck...thus exploring the possibilities.