Then, he found it. A plain text link on a forum archived in 2004:
Alchemy, Medicine, and Religion in the China of A.D. 320: The Nei P’ien of Ko Hung baopuzi english translation pdf best
Covers all 20 esoteric chapters focusing on alchemy, immortality ( xian ), and Daoist techniques. Then, he found it
Covers Confucian ethics, politics, and Ge Hong's social philosophy. Covers Confucian ethics, politics, and Ge Hong's social
via his official site, The Golden Elixir , which are excellent for understanding the alchemical terminology. Key Themes in the Piece (PDF) Seeking Immortality in Ge Hong's Baopuzi neipian
However, the circulating is James R. Ware’s 1966 translation (MIT Press), titled Alchemy, Medicine, Religion in the China of A.D. 320: The Nei P'ien of Ko Hung .
While Ware’s version is the "standard" for the Neipian (Inner Chapters), choosing the "best" depends on which part of the text you need to read, as the book is historically split into esoteric "Inner" and social "Outer" chapters. Best Full Translations by Section James R. Ware (1966) : Alchemy, Medicine, and Religion in the China of A.D. 320