This one took some research.  Contributor Bill Tibbetts ID'd the Kurtis-Buick's driver at Santa Barbara on May 18-19, 1957 as Bill Stroppe, who was a possibility, but your webmaster wasn't sure as the car was usually driven by Bill Murphy. 

A quick check yielded the fact that Murphy wore a very different-looking white helmet.

 "MotoRacing" Volume 2 #16 was the next resource to search.  It yielded the results for both days of the Santa Barbara event.  It was Bill POLLACK, not Bill Stroppe or Bill Murphy, who drove the Kurtis-Buick at Santa Barbara on May 18-19, 1957.  Pollack finished 12th in the rain on Saturday, one place behind Phil Hill in another overpowered car unsuited to a wet race, John Edgar's 4.9 Ferrari.

On Sunday, Pollack fought his way into the lead on lap 11 and led through lap 17, catching and passing Hill in the big Ferrari and eventual winner Eric Hauser in Old Yeller I.  On lap 17 Pollack burned a piston and DNF'd.