Twenty-seven years after a chilling sit-down with Ayatollah Khomeini that was one of Mike Wallace's most memorable, the veteran CBS television newsman snagged an interview this week with current Iranian President Mahmoud Ahmadinejad in Teheran. The 88-year-old Wallace had been pursuing the interview for so long that he had to be reminded by Ahmadinejad when he first asked for it. A portion of Wallace's interview, conducted Tuesday at a crucial time in the Mideast with Israel fighting the Iranian-backed Hizbullah guerrillas in Lebanon, will be shown Thursday on the "CBS Evening News." A fuller report will air on Sunday's "60 Minutes" TV news magazine. During the midst of the American hostage crisis in 1979, Wallace interviewed Iranian leader Khomeini, locking eyes with the cleric when he asked for a response to Egyptian President Anwar Sadat calling Khomeini a lunatic.