Rumors of an impending resumption of diplomatic relations between the U.S. and Cuba continue to Circulate and Mankiewicz and Kirby are but two of the Americans who have recently visited Havana to take soundings. Expansive and casually jocular, Castro seems to have put them in his pocket. ""One of the few truly electric personalities,"" says Mankiewicz of his host who went so far as to lend the Yanquis his private plane for the flight home via Nassau. ""I think my government is the most stable in the western hemisphere,"" says Fidel immodestly contrasting his ""revolutionary masses"" and well-drilled army with poor Salvador. Allende's ill-fated revolutionary fumblings. Whether he's reminiscing about the good old days in the Sierra Maestra or touting the new Cuban ""Family Code"" which was necessary because discrimination against women persists, Castro is full of studied candor as he patiently explains to his guests that no, there is not an ""opposition press"" because the Cubans don't need one and anyway ""Allende respected all these rights. The opposition press conspired."" Fidel even finds it in his Latin heart to say some nice things about JFK, who, the Bay of Pigs notwithstanding, was ""a courageous man."" They skim many subjects; nothing is pursued in any depth and there are plenty of asides from Mankiewicz and Kirby on how well and youthful Fidel is looking these days--lean belly, just a touch of gray in the beard, almost an elder statesman. Portions of the interviews have appeared on CBS TV, in Oui, Playboy and other capitalist rags.