You might be able to reach the nut with a long wrench. The top nut is only less than 6" from the bottom of the stake pocket.
Here's a pic of the bedside showing the upper nut. Like I suggested, grind the head off the bolts, then deal with the nut.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.