Eddie Van Halen may have been making a general statement about the timeline for playing clubs.
Also, in 1974, just glancing at Reisner's site, there were no apparent shows by Led Zeppelin in Los Angeles.
In 1975, the Los Angeles concerts were in March, and Led Zeppelin was in England a few days before and after John Bonham's birthday.
In 1976, there was no apparent tour anywhere; this may have been the time when the band was recuperating from unforseen circumstances.
In 1977, Led Zeppelin was in North Carolina on John Bonham's birthday, and did not come to Los Angeles until the last week of June.
Therefore, 1973 makes the most sense.