Advice on matching Ford super duty f250 to Lance 861

My 2005 F250 SC SB had the same 18" wheels but had the Camper Package with the rear overloads and stabilizer. By adding the upper and lower StableLoads, I could carry 7000 lbs on the rear axle without sag or sway. I suggest starting with SuperSprings or a heavier replacement spring pack before doing anything else. See how it rides and add a BigWig stabilizer bar and lower StableLoads if you need more support.

If you want go heavier, that's when you need 19.5's and heavier dampened shocks.