Clear out as much stuff as you can that can catch fire, since you'll be replacing the dampers anyways [I assume], heat the cast area that the bolt threads into until it's cherry red, and turn the bolt out. "Normally" PB and a good breaker bar are all that's needed, but you may need some heat if that's not working out. Another option to try first would be to try TIGHTENING the bolt to see if you can get it to move first, and then backing it out. That can help break up any rust on the threads and allow the bolt to turn out without risking breaking the whole thing off needlessly.