Abstract: A pair of removable inner side panel assemblies and a front cross panel respectively define the inner side walls and the front wall of a replaceable front compartment of a unitized automobile body. Lower rails along the inner side panel assemblies comprise: horizontal rear extensions telescopically connectible with lower socket members fastened along the undersides of the driver compartment; horizontal front portions at a higher level with forwardly open sockets; and diagonal intermediate portions between the rear extensions and the front portions to provide sacrificial bending under collision-magnitude backward forces. Upper rails are provided along the back portions of the upper margins of the inner side panel assemblies. The upper rails have horizontal rear extensions telescopically connectible with upper socket members fastened to front pillars at opposite sides of the driver compartment.