Removing a cast iron tub
I need to remove a 45 yo cast iron tub for a remodeling job 
  
  and don't want to damage the surrounding walls etc too much.


Pick one of those two, or realize that "too much" has to have quite a high threshold in this case. They don't come out easily, and they were put in before tile, etc was put on, and the  plumbing you need to disconnect may not have been provided with any access other than "bash the wall open when you need to get at it." If you are not comfortable with seeing the walls of the alcove ripped back to studs, you may not be ready to remove the tub. You can't really properly replace it without going there, anyway.