I'm mainly interested in early China and it's religions.
Have you tried Early Chinese Religion: Part One: Shang through Han (1250 BC-220 AD) and Early Chinese Religion, Part Two: The Period of Division (220-589 AD)? If you go by western periodisation, they roughly cover the ancient and early medieval eras. Following that, there's Religion and Society in T'ang and Sung China, which covers the period equivalent to the European Middle Ages. You might also be interested in:
Art, Religion and Politics in Medieval China: The Dunhuang Cave of the Zhai Family
China's Ethnic Groups and Religions
Philosophy and Religion in Early Medieval China
Religion and Ritual in Chinese Society
Great Clarity: Daoism and Alchemy in Early Medieval China
Religion in contemporary China : revitalization and innovation