Changing the alternator on my Dodge truck.  This stuff never happens in July.  Anyway, the attach bolt snapped off in the engine mounting bracket.  I had put penetrating oil on it before hand.  It has severe galvanic corrosion.  I have enough left of the threaded portion to get a vice grip on.  Any hints as to what might free the bolt up? I really don't want to drill and re-tap it.
Thanks.

There's probably no one thing that will free that bolt.  A combination of things may get it out.

Heat it and try to get it to move with the vise grips after it cools.  Apply penetrating oil as it cools.
Heat the aluminum housing and apply penetrating oil.
Repeated taps on the bolt and on the aluminum housing while using... penetrating oil.
The threads may be damaged once the bolt is out -  but you can clean the threads with a tap or insert a helicoil.

Use as little force as possible - the risk being breaking the bolt off altogether or breaking the aluminum.
Al

So, is the broken stub in the block or in the bracket?

You might have to remove the bracket and drill the broken part from the backside.

A mechanic friend showed me this trick a couple of years ago. He heated the bolt just enough that candle wax would melt on it. Melted some wax on the bolt and let it cool for a bit. The wax wicked into the bolt and it barely took anything to thread it out.

 or like Papaw said, drill from the back side, then use a e z-out, but spray penetrant from the back side 1st

Thanks for your replies.  Not one thing worked.  So it's time to drill.  Fortunately, there is enough room to get a drill in.
Anybody got a number or POC for Dodge customer support?