Although rare, if your vehicle is equipped with both a stock 4" rear block and a top mounted overload springs, longer u-bolts may be required. Order (4) ZONU4035 Dually trucks will require different rear u-bolts. Vehicles equipped with 2 piece rear driveshaft's may required the carrier bearing kit ZONF5401. Front exhaust modification may be required to clear the front driveshaft on gas models.