A method of manufacturing a frame assembly includes the steps of providing an underbody assembly (15) including a plurality of structural components that are secured together so as to be generally planar in shape; providing first and second sidebody assemblies (10a,10b) that each include a plurality of structural components that are secured together so as to be generally planar in shape; and securing the underbody assembly (15) to the first and second sidebody assemblies (10a,10b) to form a frame assembly. The underbody assembly can be formed by securing first and second longitudinally extending, closed channel beams (10a,10b) to a plurality of closed channel cross members (11a,11b). Each of the sidebody assemblies can be formed by securing a closed channel lower rocker rail (20) and closed channel upper roof rail (21) to a plurality of pillars (24a,25a,26a). Each of the pillars can be formed by initially securing a first stamping to the lower rocker rail (20) and the upper roof rail (21), then securing a second stamping to each of the first stampings. The underbody assembly can be secured to the first and second sidebody assemblies by magnetic pulse welding to form the frame assembly.