 After the weight specification was revised from to a maximum of  including oil and water, Willys-Overland's chief engineer Delmar "Barney" Roos modified the design in order to use Willys's heavy but powerful "Go Devil" engine, and won the initial production contract.The Willys version became the standard Jeep design, designated the model MB and was built at their plant in Toledo, Ohio.The familiar pressed-metal Jeep grille was a Ford design feature and incorporated in the final design by the Army.