Sergio Fascetti, Franco Merli, Aldo Valletti, Bruno Musso, Antonio Orlando, Giorgio Cataldi, Rinaldo Missaglia and Ezio Manni in Salò, or the 120 Days of Sodom (1975)
10 minutes in the movie, Sergio Fascetti and Franco Merli are forced to undress. We see their nice uncut penises and untrimmed pubes.
31 minutes in the movie, Aldo Valletti is showing his butt. He ends up being butt fucked.
39 minutes in the movie, all the boys, Sergio Fascetti, Bruno Musso, Antonio Orlando, Claudio Cicchetti, Franco Merli, Umberto Chessari, Lamberto Book and Gaspare Di Jenno are naked. They are all uncut.
42 minutes in the movie, Sergio Fascetti is naked again. We see his butt too.