New Truck Build Chevy P30 need some advice...

  Hey everyone, I'm new to this forum, although I've been reading and following it for a long time, this will be my first post. Well, I finally got my truck after looking for a long time, and we just started cleaning it out and removing the old shelves they had on the inside, but then we hit a snag. This truck has these cross bars that we didn't think were a big deal until we tried to take them down. My experience in truck automotive is very limited, and these bars look sorta like support beams so I just wanna make sure its ok for me to take these down before I go removing them. Also if it is ok to take them down, how in the world do I remove them when the nuts or whatever these are holing them in are round. Thanks for any assistance you can offer.