I completely cut my mounts in half on my BII through the rubber, through the metal bushing and through the bolt.
I replaced them all with urethane mounts.
This is the only way to get them off on the BII, the 4 body mounts under the cab are sleeved with a steel sleeve that goes throug the upper and lower rubber bushing.
You either find a larger lever that will keep turning the bolt, get some sort of a strap wrench on that bushing to keep it from spinning, or cut the sucker off!