Japanese trading house Itochu Corp. plans to acquire used car dealership Bigmotor Co. mired in an insurance fraud scandal, sources with knowledge of the matter said Wednesday. Itochu plans to take over Bigmotor’s used car sales business in the hope of bolstering Itochu’s existing automobile division. The trading house is the biggest shareholder in Tokyo Century Corp., which runs rental car services. It also counts Yanase & Co., an importer of luxury cars, as a subsidiary. Itochu also plans to ensure that the founding family members of Bigmotor will not be involved in the business operations. B…