Looks like those bolts hold the front panel to the wood bed .My 54 has bolts that close to the end but they also go through the metal strips.
On the AD series trucks, the front bed panel bends toward the rear and then down, and bolts to the front cross sill. It looks like the earlier beds didn't have the front panel bolted to the front cross-sill. You can see the bolt holes in the vertical flange of the front panel in the attached picture. The cross-sill isn't bolted in yet.
[on edit] This is probably true only for beds with angled top bed sides per kevinski's observation (below) on his '54. Mine is a '51.
