Don't know how much room you have on the outside of the bolt to work with, but maybe clamping it from the outside with - pliers or vise grips, you're not going to reuse it.
62 now, Bought my Mustang 2017 GT PP1 MT a year ago, and it's a great car.
It came with AWE track cat backs and thought it was too loud, either I got used to it and appreciate the sound or need hearing aids. Not getting hearing aids.