[Superman]

I don't think heat can help you much here. Penetrating fluid might. You certainly may need more than a 6 inch breaker bar. I have at least two breaker bars, but the only one I ever touch is the longest one, about 2.5 feet. A smooth but strong pressure is best, so use the long breaker. I know of no safer or more effective way to deal with those stuck fasteners.

I do hope all goes well though. I once heard Warren warn that stripping these particular threads (the female ones in the body, above the tranny mount) are pretty difficult to repair. Still, big breaker bar and smooth strong force is your best bet.

PS - I guess there is another alternative that may be safer but a PITA. Grind the heads off the bolts. Then you would need to remove the fasteners attaching the crossmember to the tranny. You can then deal with those stubborn long bolts later, if they don't just come right out with the crossmember gone.