Suggestions for bending rear frame horn

[SilverMiner]

I'm in the process of replacing the dented and damaged rear bumper on my 1980 Suburban. My best guess is that the bumper was beat by an unleashed trailer. Nothing fatal, but it did bend one of the frame horns that the bumper mounts to.

Does anyone have any any tips or hints on how to bend one of these horns back into shape? It is too tight to properly apply a BFH (Big F'n Hammer). I can borrow a slide hammer, but I don't thing that will have enough force. Do I need to put a torch to the metal in order to move it back into the approximate position? I have another factory bumper ready, and it doesn't need to be in perfect position, but it sure would be easier to remount if the holes lined up a little better.

Thanks for your help.