What is this ninja anime from the late 70s early 80s?
I believe you are looking for the series Manga Sarutobi Sasuke, or Ninja, The Wonder Boy.

The show tells the story of Sasuke, a Koga ninja boy living in 17th century Japan, doing battle with the Iga ninja clan lead by the evil Hanzo.1



OP/ED: http://www.youtube.com/watch?v=-b7vnd8rhoY