PB (rust) Blaster is even better. But the best I have found is a regular blue flame speed wrench. I.e. heat the fastners up to dull red hot then let it sit. You can also quench with a bit of water. Then usually that breaks the rust bond and you can un-do.

\'59 Chevy 1-ton
'72 c-10 (in progress)
The Great Rust(less) Mountain
\'47 Jeep cj2a