Engine mounting bolt - any tricks?

[tbomachines]

I've had to put my engine swap on hold for a few days due to the engine mounting bolt. I am speaking of the 8mm allen bolt with round sides that holds the aluminum mounting bracket to the mounts. This bolt was STUCK and already stripped, thanks to a PO. To get the engine out I just tore the mount in half (rubber came apart easily) but still had to get the bolt out.

To get the remaining piece of the motor mount off, I took an angle grinder and cut it in half. So what I have now is the engine mounting bracket (took it off the engine block) along with the bolt still stuck in it. I have done everything I know to do with stuck bolts...soaked it in PB for a while, didn't work. Applied copious amounts of heat while smashing on the thing in a vice, didn't work. Pipe wrench, didn't work. Vice grips, didn't work. Are there any specific tricks that anyone knows about that might get this thing loose? I would have thought that the heat would work since the bracket is aluminum and screw is steel, but no luck after lots of sweating and swearing.