Ok to heat and bend a pitman arm?

Anytime you heat metal you're altering the carbon bonds in the metal that keeps it strong. If you don't know the actual temperatures used to heat it up, how to quench the metal (in oil, water, open air quench, etc), and get the proper temper/hardness then you are in for big trouble down the road. Either too soft or too hard spells disaster. Dent the header tubes as everyone else has said. How are the engine mounts? Is the engine properly mounted/aligned? Maybe you could move the engine over 3/8". A possibility I guess.