[tmpusfugit]

You can most likely shear the heads off the bolts with a large chisel and a 2.5 pound, or larger, hammer. Or, you could center punch the heads and drill them off in pretty short order. A Dremel IMO is too small a tool to grind off the heads. You could of course use a larger hand held grinder if you can get enough access. Personally, if I couldn't take them off with the appropriate wrenches, I would go for the center punch and drill method. There is sufficent space to do that readily....I had the exhaust off 2 days ago to fit a new Flowmaster, so my experience in this area is recent!