A cargo box for a pickup truck having a header panel with integral welding braces or struts. The cargo box has left and right sidewalls defining the left and right sides of the cargo box, respectively, a tailgate attached to the rear end of at least one of the left and right sidewalls, a cargo box floor spanning the left and right sidewalls, and a header panel having a main body spanning the front ends of the left and right sidewalls to form a front side of the cargo box. The header panel has integral left and right lateral sides extending from and integral with its main body and these are welded directly to the left and right sidewalls without any intervening brace above the level of the cargo bed floor. Left and right braces are welded to the lower end of the header panel and the left and right sidewalls at and below the cargo bed floor, so that a majority of the mass of the brace is below the lower edge of the header panel.
