Yeah, your tires are most likely too wide, but before you buy new tires, put on a new set of reverse eye leaf springs and a new set of KYB shocks. If that fixes it, fine, but if that doesn't, then get a skinnier tire. DO NOT put on air shocks. Where the shocks hook up on top is a thin piece of metal, and if you have the shock too stiff, it will punch through and ruin it. DO NOT use extension shackles. They will make your rear end very unstable and you will wind up in a ditch or worse.