My guess is Paul Rickard, for these reasons; Weld quality, storage containers, multiple receiver hitch tubes and the vintage is right for the vehicle. Some of you may recall his bumpers being used on early well know projects such as the Wescott's Turtle Expedition.
Sadly, he has passed on.
If you think it was used as a race support truck, I'd post it on Race Dezert as well. As far as finding a Rickard bumper, good luck. As I stated earlier, he has past away.
I'm sure a number of fab shops would be willing to make one like it for you.
Can you recomend any fab shops here in the South West? How much was a Rickard bumper new?