I'm probably wrong but in my foggy boomer memory I think that after 790 KABC dropped ABC News. KFI actually signed for it but for some reason they never used it. Michael or someone please clarify...From 1926 until---I'm not really sure.
By 1970, KFI had ditched the network's newscasts and the weekend "Monitor" show and were simply airing the spots from within those programs. They were clearing network features in evenings, late nights and overnights.
IF I recall correctly, NBC finally jumped ship to KIIS-AM around '74 or '75---but I think that went south when KKDJ became KIIS-FM.