Can't help you too much, as I left the area in 1972 and I don't know if they were still running both the Anaheim Hauler and the Buena Park Hauler regularly by that date, or if this was an Extra Hauler which was run when there was additional traffic.

Your photo is interesting as it shows the second unit having stacked lettering, which is contrary to the painting diagram for SD9s. Do you know its number? Both it and the lead unit appear to be fresh from the paint tracks at Taylor Roundhouse.

I noticed your caption states that the haulers were "short lived." Both the Anaheim and Buena Park had been running out of City of Industry since the mid-1960s or earlier prior to being moved to West Colton, so I'm a little confused by your statement.