Best way to remove a frozen bolt for the caliper bracket?

I snapped the head off the one side- have to do the other side soon. These are 10mm X 1 heavy auto grade bolts that hold the caliper bracket on. I do not want to snap the other off. I am thinking of using a propane torch and some WD40. My racket doesn't have much leverage and I don't have an air gun. I will try to devise some type of long bar for leverage- any other tips on how to carefully get these two bolts off. The pengers side rear bolt doesn't give me much access- the front wheels at least turn. I have to try to access this bolt from behind meaning, you can't see the head of the bolt but you can feel it.