Hi!
You may try "Sword of Doom" or "Kill" from Kihachi Okamoto, both with Tatsuya Nakadai. From the 60s, very good stuff (you may have already seen Nakadai in some Kurosawa's, Gosha's and even in one or two episodes of Zatoichi!). You may try Yôjimbo and its sequel by Kurosawa, and don't forget Mifune had played Yôjimbo twice more in a Zatoichi and in a Inagaki's movie. Concerning Inagaki's movies with Toshirô Mifune, you could see all of them especially "Samurai's banner" (adapted from the Inoue's novel "the sword of the Takeda") and the trilogy about Musashi (written by Eiji Yoshikawa).
All good 60s / 70s stuff!
Nice watching!
