I suspected as much. Therefore heating the block/spacer may do you no good. The bolts are threaded into the separater rods. The separater rods are where you want to apply your heat and/or apply your PB Blaster. I would imagine that the bolts pass-through unthreaded holes in the block/spacer. You have great input in the thread above for loosening a "frozen" bolt. You just need to sort through it for your unique circumstance. And be sure to check YouTube for the exact repair on the exact piece of machinery you are working on. You may not be the first guy in this situation. (Maybe there's a repair kit?) Meanwhile keep it soaked in the loosener of your choosing right up till the coming weekend. Don't forget that it's seven years of bad luck if you break the mirror. Always wear safety goggles. Use plenty of snake oil and elbow grease and think before you act.
Now that's the best advice I've had all day! LOL
I really appreciate your seasoned overview of my dilemma and the solutions to it.