Exhaust manifold bolts

Hey Posse,

I'm throwing this question out to the general membership
hoping for good news.
My sweet little '72 Dart Swinger 318 has developed an
exhaust leak I'm pretty sure is at one of the exhaust
manifolds. Both manifolds are rusted as is normal.

The gaskets have been replaced at some point in the
past so the bolts have been removed.
My question pertains to any chronic history of the bolts
breaking off during the removal process.
I can't do this simple repair myself anymore so my
mechanic is making the repair next week.

I soaked all the bolts with PB Blaster yesterday.

As always, thanks for your input.

Tom