I think i'd get rid of the air shocks and try something else, I have always been fairly impressed with the ride of the gm 1 tons compared to other vehicles.
With the overloads I wouldnt go after an overly stiff shock, something near stock rate, I run bilstein yellows on my 2500, plan to run them on my 3500 as well. currently just have a old set of Gabriels on there.
If a softer shock doesnt help, next step would be ditch the overloads and run a airbag, no need to remove the overload perches if they arent in the way, if they were bolt in like the early ones sure, but if they are riveted on, Id leave them. run enough air to keep it off the thick bottom leaf.
Extra weight murders empty fuel economy, so I'd avoid packing extra weight if at all possible.