If you can cut a slot in it either with a Dremel or a hacksaw or my favorite all around tool "air cut off wheel" in the head of the bolt then get yourself a hand held impact wrench with a flat screwdriver bit on it. These are the kind that you hold on your hand, the bit is on the end and then you smack the butt of the tool with a big hammer. It has a spiral inside that loosenes the bolt plus the blow from the hammer wedges it into the bolt. You can get them at most tool houses and probably Northern or Harbor Freight. They work good when the part you are beating off is solid. Or you can use heat to loosen the bolt and just replace your calipers, who knows what else could be wrong at this point if someone had the intellegence to strip out the heads and then leave them... Next to steering the truck, stopping it is the MOST important. I just changed mine and they were really inexpensive. Be sure to wear safety glasses, hate to have you shoot your eye out! Good Luck. Jim.

 

Since you have mentioned, that your at a dealership one of the mechanics should have a Lisle bolt and stud remover set, if you can get one to feel sorry for you your problems will be over in less time than it took for me to post. Good Luck now you know what to ask for.

 

A trick that has worked for me a few times is to cut some wire bristles off of a wire brush and insert them into the rounded out allen head with the allen bit. The wires fills out the voids between the allen bit and the screw head and makes for a tight fit.