Republican National Chairman William Brock, a moderate that party conservatives only recently were trying to oust, yesterday was named to the Cabinet-level position of U.S. trade representative by President-elect Ronald Reagan.

Brock, 50, a former congressman and senator from Tennessee, said in an interview yesterday that attempts by some members of Reagan's transition team to reduce the status of the trade position have been abandoned and that he expects to be "very close" to the president. Brock replaces Florida Gov. Reubin Askew, who resigned last month.

The office of special trade representative was created by executive order in 1963 to negotiate and set trade policy. As part of the Trade Act of 1974, Congress made it an arm of the executive office of the president and gave it Cabinet-level status. As part of the president's trade reorganization a year ago, the office was changed from special trade representative to U.S. trade representative.

Robert Strauss, special trade representative under President Carter and also a former chairman of the Democratic National Committee, was perhaps the most prominent negotiator to hold the post, partly because of the elevation of the position's status and his close relationship with the president.

Brock said his relationship with Reagan will be "very close" and that he has "the president's support." As far as moves by Reagan operatives to reduce the Cabinet rank of the position or absorb it into the Commerce Department, Brock said, "That's behind us."

Brock said he wouldn't comment on specific issues until his Senate confirmation hearing on Monday. But he said the Japanese auto imports conflict, the negotiations to renew the multifiber textile agreement, agricultural trade, inventives for exports and unfinished negotiations as part of the Tokyo Round of the Multilaterial Trade Negotiations Agreement will be the first course on "a whole plateful" of issues this year.

As for autos, he said, "You can't help but be concerned about. The best route is not obvious yet." He added that he needs to know more about the question of whether imports of Japanese cars should be curbed to help the U.S. auto industry.

Brock also said he will probably be involved in discussions surrounding the grain embargo gainst the Soviet Union, but he doesn't know how soon such talks will take place.

Brock was a favorite target of the G.O.P. right wing because as party chairman he refused to allow party funds to be used to opposition to the Panama Canal treaties. Last June conservative Republicans attempted to remove Brock from the parpty chairmanship.

That effort resulted in a compromise in which Brock stayed as chairman but Dreww Lewis, Reagan's designate for secretary for transportation, was made the operating officer at the committee.

In addition, Brock is credited with the unexpected Republican gains in both the House and Senate last November. Republicans gained control of the Senate for the first time in a quarter of a century.