These short bed trucks have three cross sills, plus the rear main sill. The front cross sill and the one just rear from the axle have bed to frame bolts that go through. The second cross sill, the one just forward from the axle, floats there slightly above the frame and does not bolt to the frame but only to the bed strips and angle strips. Bed strip and angle strip bolts that do not align with a cross sill have the 1-1/2" washer under the boards that holds the bed boards to the bedstrip.
Mar-Ktech
