Dan Rather's Numbered Days: In 3, 2, 1 . . .

"CBS Evening News" was readying a tribute to Dan Rather for broadcast tonight that would signal his departure from the network for which he has worked for more than four decades.

As of late yesterday, the former anchor had not been interviewed for the piece, which was being worked on by CBS News correspondent Anthony Mason.

If things go as planned, this week will mark the end of Rather's 44-year tenure with the network.

Rather has worked for the CBS Sunday newsmagazine "60 Minutes," and its now-defunct midweek edition, since early last year, when he left the evening newscast he'd helmed for 24 years.

But, CBS executives recently told The Post's Howard Kurtz, they were not booting Rather because of the controversy surrounding his 2004 story on President Bush and his National Guard stint, which was based on documents that the network later said could not be authenticated.

Instead, the CBS suits told Kurtz, they have discovered that, what with Katie Couric signed on to do a half-dozen stories a year for "60 Minutes," the recent hiring of celebrity journalist Anderson Cooper as a part-time contributor and the merging of reporters from canceled "60 II," they don't have any room left for Rather pieces.

Rather last week confirmed to trade mag Television Week that "finishing details were being worked out for me to leave CBS News."

Rather had not returned a call for comment late yesterday. But he recently was quoted in other publications as saying he had formed a production company called News and Guts and was considering his options, including producing and hosting a weekly news program for Mark Cuban's new HDNet.

Rather announced he would step down from the anchor chair shortly before an independent panel concluded that CBS News had not authenticated documents used in the Sept. 8, 2004, report that alleged President Bush had received special treatment while in the Texas Air National Guard during the Vietnam War.

CBS veteran Bob Schieffer has been filling in since and the CBS newscast's ratings have been growing with him in the anchor chair. But former "Today" co-host Couric is scheduled to become permanent anchor of "CBS Evening News" in September. And the news outfit has hired Bob Peterson from NBC to oversee the "look" of that newscast.

Peterson, who late last week was named creative director of CBS News, will oversee the "look" of all CBS News broadcasts but "will collaborate most immediately and closely" on "CBS Evening News With Katie Couric," the network said in its announcement.

Peterson spent nine years as a producer-editor at NBC News in New York, working primarily on Couric's prime-time specials, "Dateline NBC" and "Today." Previously, he worked for NBC in Washington as a producer, senior editor, photographer and graphic designer.