a truck body for a light truck including a frame structure attachable to the truck chassis including invertible joists with offset cantilever ends ; truck body side walls each including a plurality of integral one piece molded plastic cabinet modules in tandem fore and aft arrangement with confronting end walls flush against each other and defining socket recesses to receive the offset cantilever ends of the joists ; one of the modules on each side having a wheel well asymmetrically located and interchangeable from side to side to accommodate trucks of different cab - to - axle spacings .