Any tricks removing rusty cab mounting bolts?

[R3500]

Any tricks to get the rear cab to frame bolts removed? This is the 73-87 body style. I want to replace the rubber mounts to level out the cab...this is a New York truck.


By the way, does anyone make the rear panel across the back of the cab..the panel at the very bottom (where it drips) is rusted through ( on the very lowest edge straight across). Must have been because it had a big box on the chassis that caught all of the road salt etc. The rockers and cab corners are solid for some reason...