When McGarrett is setting up the bust on the gambling operation, he talks with Sgt. Tatupu. McGarrett refers to him as "George". However, after the bust goes down, and Sgt. Tatupu is run over, McGarrett arrives and refers to Tatupu as "Keoki". Later when McGarett goes to see Tatupu's wife, Rose, to break the news, McGarrett again refers to Sgt Tatupu as "George".
Officer Welles' police car (1970 Ford) can be seen to have no side-view mirrors.
It is surprising that Tanaka, Palua's henchman, never recognized Mike's voice on the plane as the same one that phoned Victor Palua (Which he listened to) earlier. Tanaka would have known that the pilot and the blackmailer were the same person..
At about 21 minutes in, when the secretary answers the telephone, you can plainly see that what she says vs what is said are completely different.
It's apparent the company's name was changed to "Surf and Sand International" during filming. There are clear dubs when the former madam mentions it to McGarrett, when McGarrett repeats the name to her and, later, when the company secretary answers a telephone. However, there's no dubbing evident when Mike Welles names the company in an earlier scene.