BANGKOK, JUNE 18 -- Vietnam named a new prime minister and a new president today to replace the last of the legendary leaders who helped found the Indochinese Communist Party with Ho Chi Minh in 1930.

Pham Hung succeeds Pham Van Dong, 79, who had served as prime minister since 1955. Vo Chi Cong was appointed to the largely ceremonial post of president in place of Truong Chinh, 80, who had held the office since 1981. Within the senior leadership, Dong and Chinh were the last of the revolutionaries who helped found the Indochinese Communist Party.

Hung and Cong, in their mid-70s and also both veteran revolutionaries, were named on the second day of the new National Assembly's opening session, the Voice of Vietnam radio said in a broadcast monitored in Bangkok.

Following tradition, the top government posts went to senior members of the Communist Party's Politburo. Analysts said Hung, who ranks just below General Secretary Nguyen Van Linh, and Cong, the No. 3 Politburo member, apparently were chosen as "transitional figures" to pave the way for the rise of younger leaders able to preside over urgent economic reforms.

Analysts do not expect the changes to have any effect on Vietnam's foreign policy, marked by close ties with Moscow and a continuing occupation of Cambodia. The changes capped a year-long, major overhaul of the party and government aimed at improving the poor state of Vietnam's economy.

Dong and Chinh, the former party chief, had resigned their party posts at the sixth national party congress in December. They left after admitting "serious mistakes" in handling the economic crisis, and were replaced by Linh and others favoring pragmatic reforms, including a small dose of capitalism.

Today's brief broadcast said Hung and Cong were unanimously selected at a meeting of the 496-member National Assembly, which was elected on April 19.

The assembly also elected to the Council of Ministers Le Duc Anh, defense minister, Nguyen Co Thach, foreign minister, and Mai Chi Tho, interior minister, the broadcast said. All three moved up the party ranks at the December congress, and Anh and Tho received their Cabinet posts in a government reshuffle in February.

Hung, 75, has been a member of the Politburo since 1956 and a vice premier since 1958. In 1975, he became political commissar of the South Vietnam Liberation Armed Forces, or Viet Cong, during the final offensive that ended the war. Cong, first vice premier since 1986, was a leader in North Vietnam's key political instrument in the South during the Vietnam war.