Here's how I removed some of these bolts using a mig welder.
Preheat the end of the bolt (the easy-out in your case) with a torch. With current on high, melt a nice cherry bead onto the end of the bolt.
Preheat is a vital step in creating a strong mig weld in cases like this.
As an alternative you can weld on a washer and a nut.
Grab the cherry(or nut) with some SHARP vice grips but don't twist it yet.
Go in through the port from behind and heat the backside of the threaded boss (1 of 2 bumps) ...heat the bump cherry red with your torch and then try the vice grips SLOWLY...most of the time it'll turn out.
If not, soak with penetrating oil and heat/cool a couple times and this should get it out in a jiffy.
If worse comes to worse you can drill a 1/8 hole into the boss from behind to get the oil in and afterwards preheat the boss and zap it with the mig welder to close the hole. The mig will create a nice clean puddle over the hole if everything's clean & preheated.
P.S. be carefull not to bottom out a tap or excessively long bolt in the hole, as the cast boss breaks REAL easy....pops clean off like a mushroom cap it does....
don't ask me how I know
