Sellers not playing Kong....had nothing to do with the accent.

Notes from the War Room
by Terry Southern

"The shooting schedule, which had been devised by Victor Lyndon and, of course, Kubrick—who scarcely let as much as a trouser pleat go unsupervised—called for the series ofscenes that take place inside a B-52 bomber to be filmed first. Sellers had mastered the tricky Texas twang without untoward incident, and then had completed the first day’s shooting of Major Kong’s lines in admirable fashion. Kubrick was delighted. The following morning, however, we were met at the door by Victor Lyndon."

"It was Victor Lyndon who again brought the bad news, the next day, after Sellers had undergone a physical exam in Harley Street. “The completion-bond people,” he announced gravely, “know about Peter’s injury and the physical demands of the Major Kong role. They say they’ll pull out if he plays the part.” Once that grim reality had sunk in, Kubrick’s response was an extraordinary tribute to Sellers as an actor: “We can’t replace him with another actor, we’ve got to get an authentic character from life, someone whose acting career is secondary—a real-life cowboy.” Kubrick, however, had not visited the United States in about fifteen years, and was not familiar with the secondary actors of the day. He asked for my opinion, and I immediately suggested big Dan (“Hoss Cartwright”) Blocker. He hadn’t heard of Blocker, or even—so eccentrically isolated had he become—of the TV show Bonanza."