It depends on how many cross members you have. I am sure it was not original to MY truck, but I have two cross members. One is between the axle and the rear cross sill. It bolts to the frame and the bed wood/bed side angle strip(?). The other is between the axle and the front cross sill. It only bolts to the bed wood/bed side angle strip. On my 49 3100, I was unable to put these cross members in AFTER the major components of the bed were put together. Your truck bed maybe different.
