Eric, Shot peening or blasting shot causes friction to the metal which in turn becomes heat. Gene, those frames are much easier to straighten with heat because of accessiblity. Harley '36-'57 are a bitch because of the triangulation which made them super strong. I was taught my metal craft by really old men over many years. My father learned from his father as they worked on dressing drilling tools in the northwestern PA. oil fields Over coal fires and an anvil.I still hammer weld over that same anvil. To straighten large weldments and farm plow beams and such I was taught flame and quench. Same I was taught by an old bodyman for shrinking oil canned panels. If you haven't driven in this lane before, stay in the one you have.