[collisioncenter]

I can honestly say to this point I have never had any trouble with the cab mount bolts. However the box bolts are a different story. I know that the cab bolts are a locking style bolt that GM also puts loctite on. You say you cut it off, I would say you should be able to weld the mount to the nut from the bottom side, then take and warm the bolt up a bit, clamp on it with a vise grip and you should be able to turn the bolt out. Thats how I've taken the stubborn box bolts out that have done the same thing. When you warm the bolt up that allows the loctite to free itself. Usually does the trick.