A guy in town has 5" stacks on his lifted shortbed '03. IMHO they would look better, more proportional if he had a longbox. When he first did this mod about 8 months ago, his truck made an annoying honking sound between shifts (sounded like geese flying overhead but louder).
I was driving behind him last week and that time it sounded really good and deep, like as straight-piped 12-valver. It was also cool to see the heat waves pouring out of the tip of the stacks (no smoke at all unfortunately). The guy's an aquaintenance of a jeepin' friend of mine so hopefully one of these days we can meet and I can take pictures of his truck to post.