October 14, 1984

When he was in the eighth grade, he used to sneak into the San Diego Stadium or sometimes sell soft drinks in the upper deck. He still lives about two miles from the Padres' ball park. In the winter, he goes to the stadium every Monday, Wednesday and Friday and works out with some of the Padres. He even gets treated by their trainer. Yet, nobody has done more to shoot down San Diego's hopes in the World Series than Alan Trammell, the native son, the good neighbor, the boon companion of all those Padres, also the star shortstop for the Detroit Tigers and their most destructive hitter in the Series.

Mozart's ''Clemenza di Tito'' - an opera being slowly extricated from beneath two centuries of myth and misunderstanding - makes its Metropolitan Opera debut this Thursday in a new production by Jean-Pierre Ponnelle. Mr. Ponnelle is by rights the only man for the job; for it is he, in a series of productions over the past 15 years, who has done the extricating almost singlehandedly. The conductor will be the Met's music director, James Levine, and the cast features Renata Scotto as Vitellia, Kenneth Riegel as Titus and Tatiana Troyanos who, as a mezzo- soprano, sings the male role of Sesto. ''Tito'' has lain buried for several reasons; among them are the stories surrounding its composition - some of which aren't true. We now are fairly certain, for example, that Mozart did not write it in 18 days as traditional history reports, but in 50. Nor was he at the time already racked with terminal illness.

LONDON ON a grey London morning, John J. Phelan Jr., who sits atop the citadel of free world capitalism, the New York Stock Exchange, eased into a boxy black taxi and went calling. He met with officials at the Bank of England on famed Threadneedle Street and at the London Stock Exchange nearby. He held talks at the Salomon Brothers, Merrill Lynch and Goldman Sachs offices here. And he broke bread with international financiers at the venerable City of London Club. Mr. Phelan was a man on the prowl - posing questions, listening and sniffing out the latest trends in world finance. His mission: To expand the domain of the New York Stock Exchange to London and beyond. But the fact that the chairman of the Big Board, who hates to fly, traveled 3,000 miles to explore business here says something about the state of the 192-year institution. The day when the Big Board had an iron grip on the trading of America's stocks has long passed. It now operates in a world of pressing competition. International financial activity is expanding and markets the world over are trading new products at a dizzying pace. In his five months as chairman, Mr. Phelan has become increasingly convinced that the exchange must run fast if it is to remain the world's preeminent financial marketplace.

Bishop James W. Malone, president of the National Conference of Catholic Bishops, yesterday issued a statement asserting that the bishops had no intention of creating a ''voting bloc'' and denying that the church was involved in single-issue politics. The statement also said that politicians might concur with the bishops on Text of statement, page 30. moral issues while disagreeing over how to address those matters in terms of public policy. In recent weeks, the bishops have been accused by some critics of meddling in partisan politics in an effort to elect candidates who supported the church's stand against abortion. Examination of Issues Urged ''We do not seek the formation of a voting bloc, nor do we pre-empt the right and duty of individuals to decide conscientiously whom they will support for public office,'' Bishop Malone said.

FORT DIX DRING President Jimmy Carter's Administration, talk of virtually closing Fort Dix as an economy measure buzzed through this Army post in central New Jersey. Now the talk has quieted - some say, for good. ''Our unofficial slogan of late has been 'Dix Is Back,' '' said Dick Dowling, a spokesman for the fort. ''I don't judge or explain Government policies. The fact is that we have commitments, and that's enough for us.''