The bolts are staked from the back side. Use a cutoff wheel in a small angle grinder and slice off the end of the bolt that sticks through the bracket inside the crankcase. Heating the round bolt head cherry red also releases the torque on it. A pair of vise grips on the screwdriver shaft helps, also. It's easy for anybody with a lathe to make a stub shaft to align the bracket in a different block.
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!