I need help trying to remove bolts, whose heads have easily broken off in engine.?

I recently changed my thermostat sensor, which has been broken forever. I noticed it was broke after I came back from a year long deployment about a few months ago. Once I changed that, apparently I had been driving my truck at a very high temperature. I figured I'd change my thermostat, but that's been an adventure. Both of the bolts to the thermostat housing snapped off. Once we removed the housing, I figured a lot of PB Blaster would loosen it up and vice grips would be able to turn it, but they aren't working at all. Since than I've tried tapping it, using those ridiculous gripits(Which snapped immediately). I cant afford to pay a mechanic out here, and the truck isn't drivable at all now. Any ideas?