Dremel two flats on the outside of the fawked bolts, use a pair of big locking pliers to grab the bolt, then use another pair of locking pliers to turn the first pair. If you orient them the right way, you can also slip a pipe over the handle of the second pair without releasing them to get more leverage.
You can also try a damaged nut removal socket if you have a set.
Oh right, and spray the things with PBlaster repeatedly and let it work into the threads overnight before touching anything.
If none of this works, buy/beg/borrow/steal a wire-feed welder, weld a nut or bolt to the bolts, and use a socket to turn the new, unbuggered head.
