The top hinge has a center bolt from inside of pocket and threads into a floating captive square nut. Nut is held in place by a sheet metal surround to keep it from turning while floating. If broken or turning maybe take off inner fender or fender or try reach in from under truck.
Bottom hinge has a center bolt from outside into weld nut on hinge.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn