I got the exhaust manifold studs out, finally.... remember I had to saw off the nuts on two of them, as well as two of the bolts that broke off.
JM said to try wedging two nuts back to back, and turning against each other. I tried that, but quickly stripped one of my two nuts 

So then I invented a new technique, I used one nut and 'mushroomed out' the end of the bolt/stud by beating on it with a hammer. I then backed out the nut, which was then locked in by the mushroomed end. Very clever, unless you want your nut back...... 

And there was still one too short for all this, so it had to be drilled out. I will have to get a tap and rethread the hole, anyone happen to know the bolt size, metric I suspect. Looks like 20 threads per inch.

Needless to say, I will be getting new studs, bolts, and threads.