The announcement comes days after a hand injury forced middleweight champion Luke Rockhold to withdraw from his bout with Larkin. It was the second time that an injury led Rockhold to pull out of a fight against Larkin.
The hard-hitting Larkin, who has a professional record of 13-0 with one no-contest, will return to action for the first time since a July 14 unanimous decision over Robbie Lawler.
Souza will bring a 16-3 record and two-fight win streak into the cage against Larkin. He registered an impressive first-round knockout of Derek Brunson in his most recent bout on Aug. 18.
Moussasi (32-3-2) has not fought since December 2011 when he earned a unanimous decision over Ovince St. Preux.
Kyle is 19-8-1 with two no-contests as a pro.
During his most recent bout on May 19, Kyle was submitted in the first round by Rafael Cavalcante. But the outcome of that fight was changed to a no-contest when Cavalcante tested positive for a banned substance.
Cavalcante, a former Strikeforce light heavyweight champion, is currently on a one-year suspension by the California State Athletic Commission.