This weekend I finished a two week fight against the two M12 x 180mm bulkhead to chassis bolts. They had to come out for a rock slider install.
I estimate I spent over $700 trying to get them out. New tool purchases, bottles of penetrating oil and Mapp gas will do that to 'ya.
In the end, I purchased the air hammer known as 'Big Nasty.' I should have done it sooner, because that did the trick pretty easily. The key is to heat the bulkhead sleeve where the bolt passes through. The chassis outriggers are not where the bolt is seized, as the bolt has an air gap in that area. Mine were extremely thin in the outrigger area. Rust had eaten them away. Heat the bulkhead to a glow, slap them on the threaded end with 'Big Nasty,' and out they'll pop.
I used replacement bolts from McMaster Carr in 10.9 with cad-plated nuts and washers.