just thought id throw this in
theres a guy who lives around me who hauls cars with his ram 3500 chassis cab i believe, either way he has a western hauler type bed on the back. he's got what looks like to me a 100+ gallon tank retrofitted from a semi truck mounted behind his cab he was filling up yesterday at the gas station i was filling up at. he was hauling 3 new silverados on his wedge trailer and what caught my attention was the fact that his truck was sitting level. so i asked him whats he doing to keep i like that he showed me these huge airbags he had mounted inside the frame i cannot remember the name of the kit but the springs were sitting about an inch away from the overloads. now clearly he was hauling over weight i used to have the same trailer and it weighed around 7500lbs dry via the cat scales near my house.
so larger bags is what i would recommend with keeping in mind they don't add to your gvwr