Center punch a dimple in the bolt heads as close to the middle as possible, then use a drill bit to remove the bolt head. I'd use about a 5/16" bit or so. Once the bolt heads are close to gone, try using a hammer and chisel to knock them off the rest of the way. There should be enough left of the bolt shanks to remove them with a pair of vise grips once the wheel cylinder is removed.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!