broken bolt on thermostat housing

I need help! To make a long story short my brother-in-law (who couldn't fix a broken shoelace let alone a truck engine "even a simple chevy 350") broke the stud off about 3/8" above hole. By the way, the water pump was the problem, wich was pretty much pissing all over the drive way. Now to the problem, how do I get it out? I've tried PB blaster w/ vice grips, no i didn't round it off, and I tried gently heating it with a propane torch and vice grips. I ,of course, tried putting a nut on it before that no luck cause there was a shouder? Not a stud? Hmmm! Now I'm at a loss. Any suggestions?  

Try quickly heating the metal around stud very hot and they cooling stud with a piece of dry ice  and quickly try to remove it. The heat will expand bore and the dry ice will shrink the stud.

That may work but I have to be careful because the manifold is cast aluminum. I will try it though.

Well aluminum swells or axpands quicker than steel or cast iron so if done properly as stated above it should loosen the grip on the stud. Do make sure to lube a replacement bolt with a bit of grease before you install it. I never replace/install a bolt dry.

I had this problem on my Land-Rover SII, the way I got the stud out was to borrow an arc-welder and weld a bolt onto the top of the stud; when it was cool, I just unscrewed it out of the housing. Hope this helps.  

i would try snowmans technique and for a head if you have enough room lock two nuts together and try it that way