Moderate heat won't hurt anything. It may allow enough expansion to get the roll pin to break free it will also create capillary attraction that can draw your' penetrating oil into the bore, and help loosen it. Sometimes it just takes a few days for the penetrant to work. I prefer liquid wrench to WD40.
A little Berz-o-matic propane torch is almost foolproof, because it can't generate enough heat to damage anything. Oxy-acetylene torches must be used sparingly.
Also make sure that the casting is backed up well, with something considerably heavier than the hammer of your' choice. Wood will absorb some impact too, so if you're cushioning it with wood, it might be defeating the purpose. If there is any flex upon impact, then it is absorbing the impact, and it will not be concentrated on the roll pin.
Nice truck by the way.... good luck!
