broken motor mount bolt
 

Any advice on how to get a broken motor mount bolt out ?The remaining steel bolt seems to be frozen in the rear of the front aluminum angle mount.I tried solvent, drilling,dulls the bits,I tried lump hammering w/a drift pin, Tried a stud extractor,but no room to rotate the extractor.Next will try two nuts locked together,and some heat. Anything else to try? Running out of options. There are still two good bolts remaining on the same side. 1996 35 lightning twin 500's Thanks