The stock bolts in my 54 bed had a philips head making it very difficult to try and remove. As discussed twisting them off was the easiest in the end. If you decide to try and remove them add a little heat to the nut before you try to remove it, If you are working alone, you can tack weld the head in place if you dont mind the minor scaring to the bed. It is easily cleaned up with a grinder/sander after. They come off pretty easy and quick, but chances are you are going to get dirty, wear a hat and safety glasses.
