I went out and got myself one of those Oxy/Mapp torch kits. I have been applying heat and PB Blaster to this thing for couple of days now, and the damn thing still won't budge.
I'm beginning to think I'm going to have to take the engine to a shop somewhere and have them go at it with a bigger torch, or some other means.

 

Add oxygen until you get a bright white flame with a blue tip, and it hisses like a rocket. Mapp gas will be hot enough to cut the stud off, so be careful. Learn to read the color of metal.

 

Well, after several heating cycles and a whack of PB Blaster, I finally got the heat exchangers off the motor.
I went through 4 canisters of Oxygen and a nearly a full tank of Mapp gas doing this.
Now I'm on to stud removal.
Wish me luck.