I came across a file which includes an audio recording of a BBC Radio 3 program titled "Understanding McLuhan" which broadcast November 25, 1981. I haven't listened to the tape yet, but there's a letter from the BBC which states they wanted Ong "to record about 20 minutes of material which would be a mixture of personal reminiscence and analysis of McLuhan's work with the emphasis on the latter." In particular, they were looking for an "account of the genesis of McLuhan's ideas and an assessment of the importance of his Catholicism to his thinking in general." The letter is dated 21 April 1981. Ong notes that he did the recording on 29 April at the studio of KWMU, which is St. Louis's NPR station.