"Regarding Phil Hill in the Ferrari, I looked in his book, 'Yankee Champion' and there is a photo of Hill in that same car racing in a very wet event at Pomona Fairgrounds in 1957.  That would fit with the grandstands in the background of the Tibbetts photo.  Hill raced a #2 Ferrari Monza at Pomona Jan. 19 (1st) and Jan. 20, 1957 (retired) according to 'American Sports Car Racing in the 1950s'."

(7-24-08)  From historian Ron Cummings:

"The Hill photo in the rain is Pomona in Jan or Feb of 1957. After spinning out three or four times while in the lead, Phil parked the car. He told his crew he was tired of making an ass out of himself.  Jim Sitz, Phil's friend, told me that story.  I was there on the back straight."

(12-1-13)   From author and historian Jim Sitz:

Photo of Hill in the Ferrari Monza at the very wet 1-19-57 Pomona event.