Terence A. Todman, the U.S. ambassador to Costa Rica, had the inside track and appeared only a step from the finish line yesterday in what has become a frantic race for the once-unglamorous job of assistant secretary of state for inter-American affairs.

Todman, a black career Foreign Service Officer who was born in the Virgin Islands, flew to Washington yesterday to meet with Secretary of State-designate Cyrus R. Vance, and his appointment seemed all but certain.

Former presidential candidate and Office of Economic Opportunity head Sargent Shriver, Notre Dame President the Rev. Theodore Hesburgh, at least a pair of other ambassadors in Latin America, an assistant director of the United Auto Workers and others were considered for the post.

Early interest came from liberals determined to put one of their own in a position to prevent U.S. policy from returning to what they consider the interventionist mode of the Nixon years.

Much of the excitement about the selection for a job for which past administrations sometimes had trouble finding takers also resulted from a new determination by Hispanic Americans to have representation in high levels of the administration, a determination fueled by Jimmy Carter's promises to the Hispanic American community.

Esteban (Ed) Torres, 47, assistant director of international affairs for the UAW, campaigned hard for the post, which would have made him the first Hispanic American to get a top job in Carter's administration.

Late yesterday as Todman met with Vance, Torres was seeking an appointment with Rep. Dante B. Fascell (D-Fla.), an influential member of the House International Relations Committee.

El Congreso, the national Congress of Hispanic American Citizens, decided to push Torres' candidacy during a meeting in Kansas City in December.

At one point a lobbyist whose sole job was promoting Torres was working out of Sen. Alan Cranston's (D-Calif.) office.

Manuel D. Fierro, president of El Congreso, testified yesterday at Vance's confirmation hearing that Torres was the single outstanding candidate in the eyes of the 16 million Hispanic Americans he represents.

"We are aware that career Foreign Service officers look upon a transfer to the inter-American bureau as being tantamount to a sentence in Siberia," Fierro told the Senate Foreign Relations Committee hearing.

"We realize that the position of assistant secretary of inter-American affairs often has been difficult to fill, because prospectice candidates are repelled by the lack of posibilities of doing a really effective job," he said.

He promised that the Hispanic community would not allow this to continue. It 'is a sleeping giant no more," he said.

A Capitol Hill aide suggested yesterday that the pressure from Hispanics had made it almost impossible for Vance to name a white male to the post.

One of Torres' campaign managers, told of Todman's strong position, said the choice of a black was "a very clever flankeroo."

The ethnic pressures in the contest were also mentioned by one lesser known white candidate who still had hopes yesterday and said: "The length of the selection process is related to the pervasive Hispanic campaign and Vance waiting until other Latins had been named to high-ranking jobs in other departments."

Carter transition workers acknowledged that "there was no breathless rush" to fill the job because of the conflicting pressures.

The first decision made was to oust the incumbent assistant secretary, Harry Shlaudeman, a career Foreign Service officer who was deputy chief of mission in Chile during the U.S. campaign against Marxist President Salvador Allende.

In his campaign, Carter strongly attacked the secret U.S. role in working against the Allende government.

Carter transition aides then surveyed Latin American experts inside and outside government, trying to find out what the needs were for the job.

In a meeting with Hispanic American leaders Monday, Vance told them he wanted someone "whose credentials on the human rights issue were impeccable; who has no past relationship with intelligence agencies and that he be a tough, effective administrator."

Human rights abuses in Chile, Argentina, Brazil, Cuba and some Central American nations have drawn criticism in the United States and around the world.