The political heirs of slain President Park Chung Hee are devising a succession plan they hope will assume their continuance in power and defuse objections from opposition leaders, sources here revealed today.

The plan, which envisions Park being succeeded by an elder statesman figure who would promise to lead South Korea toward gradual reforms, also is meant to satisfy the nation's powerful military leaders, who are known to distrust most prominent politicians in the government camp.

The plan, however, appears headed for a rough ride from opposition political leaders, the chief of who said today that Park's successor should be chosen by direct, popular election.

In his first public comment since Park's assassination, Kim Young Sam predicted that there would be little popular support for a successor chosen under the indirect method required in Park's constitution and used to ensure his hold on the government.

"If they try to stick to the old system, it will create a very serious situation," Kim said in an interview this morning. "People will not support the present system."

The purported compromise plan, revealed today by sources, would select the nation's next president by the indirect method. The sources added that the successor would have to be a trusted, politically unambitious person who could appeal to diverse groups, including the political opposition.

The plan, which will not be unveiled publicly for at least several days, is believed to have broad support within the Democratic Republican Party, of which Park was president, and among the National Assembly bloc of 77 members personally appointed by Park to ensure his control of the 229-seat legislature.

Park's constitution prescribes that the president be chosen by the National Council of Unification, a 2,600-member body elected last year in a controversial and widely disputed election that voted overwhelmingly to give Park another six-year term.

Opposition leaders in the past have demanded that the old constitution be scrapped and the president be elected directly by the people. Kim and other politicians in the period following Park's death have reinforced government appeals for national unity.His comments today spelled out the details of how he sees South Korea's political future and they differ substantially from the gradual pace of the government plan.

Kim said that the constitution should be amended as soon as possible to provide for direct popular election and if this were not possible, it should be amended to delay that election for several more months.

He also said that future presidents should be limited to a single, six-year term. Park had had the constitution amended to permit a president to serve unlimited terms.

Kim asserted that the country's past political troubles stem in part from leaders trying to hold on to power for too many years.

Kim also suggested that Park's assassination came about because, in part, he had been in power too long.

Kim had been ousted by Park from the National Assembly because of his strident criticism of the government, at one point calling Park's rule "dictatorial."

His ouster led to the walkout of Kim's 66 New Democratic Party colleagues in protest and was a factor in subsequent street disturbances that observers believe contributed to polical tensions that ended Park's rule.

Another major factor for the interim government to consider is where the military would stand. Since Park's death the military has expanded considerably its power base, taking over the Korean Central Intelligence Agency and administering martial law. Its political views on the future have not been made known, although one source said, "I don't think the military would object to this plan so long as the successor is not a politician with big ambitions."

Kim said today the military should remain neutral in the matter.

Military suspicion of many government politicians is well known. Two close friends of the late president -- Kim Jong Pil and Chung Ii Kwon -- have been mentioned most often as possible successors if the old constitution is followed. An informed source said today that neither would be acceptable to military leaders.

"They are too political," the source said.

Park's heirs hope to get around military objections by putting forth a distinguished figure with no political ambitions. The sources declined to say which person or persons they would suggest if the plan meets a favorable response when it is announced.

They had hoped that their plan would appeal to opposition forces with its promise of eventual "political evolution" in the direction of reform. The candidate would be required to state his views specifically on that question. "He would make it clear that he will do his best to carry out a program for political evolution without destroying stability and security," one of the plan's authors said.

Supporters of this plan contend it would be impossible to take all the necessary steps to ament the old constitution to provide direct elections before Park's successor is chosen, in about 80 days.

Those opposition leaders who have suggested amending it, he asserted, are proposing to "destroy the basis of our stability."

The plan in its final form is not expected to be announced until after investigators from the martial law command have issued their final report on the assassination. This has been expected for the past five days.