[Richard]

Had to cut off shackle bolts with a cutoff wheel on my 72 because they were rusted in place. Heat would not have helped much because of the rubber. If I was in your situation with the older truck and solid bushings. I would remove the nuts and zerk fitiings, heat the outside of shackle until red and pound the bolt out with a drift. Heat will work. Recently got some hinge pins out of a 62 VW van door using this method. Was pretty quick. Watched some videos of people using expensive tools to remove the hinge pins with no success. The tool broke in one video. Obviously, there should be no weight on the joint while doing this.