The plane at the top is the Xian H-6I, which was to test the possibility of equipping an H-6 with 4 engines, the one in the middle is the Xian H-7 (WS-6J powered version), while the bottom plane is a version of the Xian H-7 with six turbofans. The H-7/H-8 designations were in some books misused for the H-6I, but the H-6I was a different plane than the H-7 design, and Andreas Rupprecht's book Dragon's Wings adds more info about advanced derivatives of the H-6.