Don't know what year car you have. but my 65 has very light stamp marks in the rear floor where the factory had stamped the mounting position for the floor plates like the 67 uses for there rear seat belts. These stamp marks also have the punch mark for the punching for holes or spot welds. You may look for them on your car . But if your car is undercoated or dirty you may not see this so well. I will post picture.You will have to make a plate to reinforce the floor to keep the bolt from ripping through. I event you drum brakes fade out and you wreck.
