Suspension mod's to carry 2005 1181 Lance

Thank you everyone for the responses as now I know the truck can handle the weight readily with few modifications to the suspension. I have timbrens on my 1500 GMC now and know what they are, how they work and what they cost and I am happy with the results. I am familiar with what I believe are upper Torklift Stable Loads to cause to engage the overload spring earlier under load and that the Stable Loads can be swung out (disengaged) when under no load. I am not familiar with what are Torklift lower stable loads? Can anyone enlighten me? In addition, is it likely that I will need a sway bar (where does it go and what does it do)?
I just read Sleepy's post this week and wondered if adding another leaf to the rear spring packs wouldn't address these concerns in a similar manner? cheers