Have the 4 3/4" head bolts loosened up so I can slightly move the brackets. I am having trouble getting the bolts all of the way out. I've tried ratchets, as well as an impact. My thought is that there is likely a u nut on the back side, in the frame rail that is broken. Thus the bolt just spins. If that is not what secures them to the frame rail, how am I supposed to get to a regular nut inside the frame rail? Thanks