Cab bolts are "blind" and accessed from underneath the truck. Floating nuts captured in the body. Bed uses carriage bolts, so only the nut underneath is *supposed* to loosen up.
Not sure if they welded in the bed bolts on trucks, they did on K5's. In any case, taking a cutoff wheel (or similar) and cutting slots in the head of the bolts can come in handy for tightening, if you can have someone help you when you go to tighten them.