If the car has been in Kansas all it life most likely then you have way more rust issues then I have in Oregon. No salt on roads around here. You may also need to use a torch to heat the bolt to get it out. It doesn't take much to spin a cage nut. If you need a trunk pan then most likely the cage nuts there are already loose and will not allow you to take the two bolts out in the rear. There is only 3 on each side and two in the back and two up front by the core support. You don't have to lift the hole body up at once and just do a side at a time. Floor jack and a flat piece of wood under the floor pan brace should allow you to pick it up just enough to slide in the new bushing.