Mo. Rev. Stat. § 304.174

The provisions of sections 304.170 to 304.240 relating to height, width, weight, length and load restrictions for motor vehicles shall not apply to any wrecker or tow truck performing a wrecker or towing service, as defined in section 301.010. If a disabled or wrecked vehicle cannot be moved by a wrecker or tow truck, a rollback or car carrier, as defined in section 301.010, may be used without regard to such height, width, weight, length and load restrictions, if it is a bona fide wrecker operator or owner.