Moslem clergymen were winning almost every seat today in early election returns for an assembly that will study a new constitution to shape the future of this troubled land.

Elections for the 73-member assembly were held Friday. Of 417 candidates, 383 were mullahs, or Moslem clerics. Returns from Qom, Semnan and other cities in and near the central province showed that nine of 10 seats allocated to the area were won by mullahs. Final results are expected to be announced Monday.

But Ayatollah Sadegh Khalkhali, head of Iran's revolutionary courts and the man who called for the assassination of the ousted shah, apparently failed to win election to the council. An early count gave Khalkhali only 90,680 votes to 392,491 for Ayatollah Morteza Haeri and 259,537 for Hojatoleslam Lotfollah Safi.

The two winners will represent Iran's Central Province on the 73-member council.

Khalkhali based his campaign on the fact that, as head of the revolutionary courts, he sent about 200 people to the firing squad, including former ministers and army generals.

Ayatollah Ruhollah Khomeini, the religious figure who led the Islamic uprising that toppled Shah Mohammad Reza Pahlavi last February, had called to the people to vote for candidates who are true to Islam. Many secular political groups boycotted the elections, saying the procedures were undemocratic and did not guarantee a fair election.

The balloting was conducted with little of the privacy to which Westerners are accustomed. Officials wrote personal data about the voters on a form and voters were told to write in the name of the candidate they wanted on another section of the form. Officials at several polling places in Tehran said they saw many people voting for the mullahs.

The new constitution will replace the country's first charter, which was ratified in 1906. The assembly is expected to follow Khomeini's policy and make Iran a religious state in which most power will be in the hands of the clergy.

In addition to Moslems in the assembly, four seats have been set aside for religious minorities, including Christians, Jews and Zoroastrians.

Although precise figures were not immediately available, Interior Minister Hashem Sabaghian said voting was lighter than in a March 30 referendum at which Iranians opted for an Islamic republic and ended the monarchy. In that election, officials said 20 million Iranians voted.

"People cannot be expected to come out in the same numbers for the election of an assembly as in a referendum," Sabaghian said.

Violent clashes were reported to have taken place at several of the 18,000 polling stations throughout the country. Pars, the official news agency, said five persons were injured in clashes between rival political groups in the village of Deh Kohneh, and a mob attacked a polling station in the village of Gasht and made off with the ballot box. Both villages are in southwestern Iran.

Meanwhile, Foreign Minister Ibrahim Yazdi was quoted in the newspaper Kayhan as saying Iran was willing to sell back its F14s to the United States "or any other country willing to buy them from us" - a comment interpreted here as a threat to sell the 78 warplanes to the Soviet Union if the United States does not agree on a price with Iran.

The U.S. State Department said Tuesday that the United States was trying to buy back the planes, but had not reached an agreement yet. The State Department has told Iran it is unwilling to refund the full purchase price of $25 million each.

Yazdi said keeping the aircraft would involve a maintenance expense of about $500 million a year, and the presence in Iran of "at least 400 American advisers, something which would make us dependent on the United States."