You can reliably straighten it with the tool you see in the 6th minute of this video.
https://www.youtube.com/watch?v=01RnS6G6t30
If you don't have a chance, cut, knock, weld. But maybe someone will have an idea. I don't know how hard it is after all these years. Maybe burn out and knock.
I used a similar method on stainless steel. There was no other option. The bulge did not go down otherwise. There was no room for shaping.
