[Mr. Pink]

PB Blaster is good stuff. I use a small plumber's torch and get the bolt red-hot. You ought to take out the distributor though and move as much wiring/hoses out of the way as possible. A few love taps with a punch and a hammer help as well to get things broken free. Worst case scenario, pulling the lower manifold isn't hard. If you end up doing that, run a thick bead of Black RTV instead of the little front and rear cork gaskets.