I've taken a number of pitman arms off in my day, and a little heat seems to do the trick. I take my mapp gas torch and heat up the arm just a little bit, taking care not to damage the shaft seal. I use a decent quality puller, a little heat, and hit the end of the puller with a hammer, and it's always worked for me. A little PB Blaster, or equivalent, doesn't hurt, too. Never had to cut one off with this method.