The database lists the referee and one of the other judges. The third judge was Dominico Carabellese.
Source: AP via Corpus Christi Caller Times, May 8, 1971
(The paper spells the first name as "Domenico," but I'm using the spelling according to the database; Carabellese refereed Benvenuti/Luis Rodriguez. The paper lists the three officials and states that the referee would be chosen from them.)
Monzon/Benvenuti II.
Re: Monzon/Benvenuti II.
Thanks, and the correct name was Domenico indeed 
