[collisioncenter]

I'm not exactly sure how those cab mounts are mounted in the cab, but thinking about how I've done things like this in the past...I would take a cut off tool and cut a door in the side of the mount to access the nut that has broken loose. Then weld the nut in place so it won't move and try like I said in my previous post. Once its out and your confident with your weld on your nut (so it won't break loose when you install a new bolt). Close the door you cut and weld it shut. Good luck with it, most of the time these things we make a bigger deal out of in our minds then what it actually takes to do the project. You'll do great!