I'm not familiar with Japanese Westerns, but here's some Chinese movies that have a strong Western influence-
Return of the Chinese Boxer- really fun movie. The guy in my avatar has a special surprise. I don't want to give it away ;D
Peace Hotel- not one of Chow Yun Fat's best movies, but it's decent.
Dragon Blood- this one is pretty bad. The bad guys can't seem to pull their guns out before getting kicked by the hero.
Trinity Goes East- I've never seen any of the Trinity movies but Videoasia says that this is "the last and best incarnation of the Trinity franchise". Somehow I doubt that. It's a really stupid movie, but it's fun if you are a fan of both SW and kung fu.