Some leading conservatives took a critical look at President Reagan's record during his first two months in office yesterday and could find little with which to disagree.

In an informal report card, the conservatives' spokesmen gave Reagan an "A" on ideological purity, a "B" on policy implementation and a "C" or lower on appointments. But even here, the graders conceded the president is beginning to show improvement.

"Unless we are chronic complainers, this administration has to look pretty good," William A. Rusher, publisher of the National Review magazine, told a Conservative Political Action Conference here." "We will never again have a president of the United States who is as an identifiable, outspoken and effective movement conservative as this one."

"On both domestic and foreign policy it is very difficult to fault the administration from a conservative point of view," said E. Stanton Evans, another longtime conservative journalist.

But Evans and other conservatives gave far poorer marks to Reagan on his appointments. The administration, he said, made a fundamental early mistake in seeking professional managers rather than conservatives campaign workers to fill important jobs.

"It is very difficult to implement a revolutionary or counterrevolutionary policy with people who are essentially business-as-usual managers," added Evans, director of the American Conservative Union Education and Research Institute. He singled out the State and Defense departments for making particulary "bad appointments" from the conservative viewpoint.

Other speakers expressed general agreement. But their remarks were less critical of Reagan than those made by direct-mail expert Richard Viguerie at the beginning of the conference on Thursday.

Reagan's oldest supporters "can hardly get the time of day from the White House," Viguerie said. "People who have been supporting President Reagan all these years are just having a hard time. But if you were an establishment Republican involved with Nixon, Ford or Henry Kissinger, you seem to have a pretty good chance of getting a job."

The harshest warnings yesterday came from Howard Phillips, chairman of the Conservative Caucus and a former Nixon appointee. He expressed disappointment that Reagan had not tried to balance the federal budget this year and said the president lacks a coherent strategy to get his program passed.

"What I fear most is the momentum of November may be lost," he said.