If heavy duty means "lets you carry more weight in your bed and tow more" do not do it unless you actually have weight in your bed or tow a lot. To do this, the springs have a higher spring rate which makes the ride very hard unless you're loaded.
I think this is the guy from a week or two ago that lives in Alaska and has a bunch of rot under his truck. They said the leafspring eye was completely rusted through with a bunch of other stuff. Road salt is the worst on vehicles.