Two high-ranking Justice Department officials scheduled for replacement by the Carter administration have been asked to delay their departures until completion of some major criminal investigations under their direction.

The officials are Assistant Attorneys General Richard L. Thornburgh, head of the Criminal Division, and J. Stanley Pottinger, who heads the Civil Rights Division.

Pottinger has been in charge of a New York grand jury probe into burglaries committed by the FBI against political dissidents during the early 1970s.

Thornburgh has been in overall command of the investigation into charges that some members of Congress took bribes from the South Korean government. He also is involved in a separate probe of the FBI concerning allegations of abuses of power by some bureau officials.

Attorney General Griffin B. Bell is known to be recruiting replacements for both men. However, Justice Department sources said that Bell, in the interest of continuity, wants them to see these much-publicized investigations to their conclusion. Both probes are believed to be several weeks, or months from completion.

If they agree, the sources said, Bell's tentative plan is to give them a special, temporary status allowing them to concentrate exclusively on the investigations.

According to the sources, Thornburgh has agreed to this plan. Pottinger, the sources added, had been preparing to go into private law practive, and it is not clear if he will be able to put off his departure.

Pottinger's replacement in the Civil Rights Division has been identified by Justive Department sources as Drew Days III, an attorney with the NAACP Legal Fund. The leading candidate to head the Criminal Division is believed to be G. Robert Blakely, director of Cornell University's Institate on Organized Crime.

Following a six-month trial period the Federal Bureau of Prisons yesterday made permanent its policy of allowing reporters to interview inmates at the 37 prisons operated by the U.S. government.

Under this policy, reporters can conduct face-to-face interviews with any of the approximately 27,000 federal prisoners willing to talk with the press.

The policy was instituted on an experimental basis July 1 after a 46-year ban by the bureau on interviewing of inmates.