Brett:
I had the same frustration when I found that one of the torx T40's which hold the cam position sensor on the back of the cam cover on my 960 (B6304F) was wrecked. And believe me, you would not want to use a torch back there!. A vice grip also would not work as there was insufficient room. I was advised by the mtc. manager at the Volvo shop in Surry BC (whom I trust implicitly) to use a small cold chisel and a hammer, striking teh buggered head at an angle that is conducive to its 'unscrewing'.
Absolute sacrilege on an aluminum engine, I thought.
But I did it anyway, being that the closest Volvo dealer is 16 hours away, and I wouldn't trust any of the bozos around here to fix my wheelbarrow.... tap tap tap tap and on and on and on..... And eventually the sucker freed up!
If you have the room to swing a small hammer, try it. The incessant impacts make the difference.
JD