Some of the used BIG REDS I have purchased have bent cargo racks. This is typically caused by a crash as opposed to overloading the racks. Straitening the racks is pretty straightforward for me. I use an oxy-acetylene torch setup with a heating tip. Anytime you use a torch safety is key. If you are beginner find someone that has safe experience with torches to show you before you attempt this on your own. Before I start I get a plan together. You will need to analyze the rack to determine where you need to heat the rack to get the rack straightened. Next you need to determine whether if you can keep the rack on the vehicle or not. Again safety is key here. If possible I like to straighten the racks with them firmly mounted on the machine. I say this because having the rack on the machine gives you a good perspective as to how far you need to straighten it so it looks right. I use welding blankets to protect the BIG RED however you may need to remove some components. In this case the rear fenders were removed. Next you will need to plan how you are going to bend the rack. This can be done by hand or pry bars may be required. You should have an initial plan and a backup plan since you will have a limited time when the heating steel will be easy to bend. I will heat the area of the rack that needs to bend red hot and then I will bend it strait. This may take several attempts. You will burn the paint off of the rack so it will need to be repainted. You could use other means to straighten the racks like using hydraulic power (press) but for me I have had more success with heating.
Heating the rack
Before
After