In the first scene with the news stand, the headline on the Los Angeles Times reads "SLA tells of plan to free Patty [Hearst]" indicating this was shot in the spring of 1974.
The magazine at the newsstand with Paul McCartney on the cover is the April 1974 issue of Circus Raves Magazine.
This episode was adapted for a paperback novel, "MANNIX #4: Round Trip to Nowhere" by J.T. MacCargo (actually hardboiled author Peter Rabe). In the novel, which may have been based on an earlier draft of the script, Mannix has a different relationship with Jenny Cole and her doting mother. Jenny is virtually a stranger to Mannix, hired by her doting mother. In the television episode, Mannix was friends with Jenny's father.