My strong preference is moly lube for stuff like this

Preference or not, it is not the correct thing to do. You can't get the same stretch, because you have no way of accurately measuring the stretch of a head bolt, at least on these engines. And, even if you could, you have no spec for it. You *might* get away with it on something like a rod bolt, but...again no spec, just a torque value.

Once you add a lubricant where it is not speced for, the torque value is worthless. It will take waaaay less torque to get the clamping force the factory is calling for and if you go to the spec'd torque, you run the risk of over torquing the bolt or over compressing the gasket. Either of those will most likely cause a HG failure.

Also, let's think about the definition of "tight". I would bet a boatload none of the head bolts, in either of the above two accounts, were tighter than the factory spec of 47 lb-ft for the larger bolts. Now...the breakaway torque was much greater because of the friction between the bolt and the head and the threads and the block. They may be buggers to break free, but they were no tighter than what they were supposed to be. Most head bolts I've ever removed popped when they finally broke free.

As for removing the broken stub, I just remembered there is a good thread around here from a while back outlining most of the more common options, along with various tricks and tips, available.

Good Luck.
Michael