Bucknum drove the Wexler T70 at Riverside 0n October 31, 1965 as #12.  He was a non-starter.  This doesn't look like Riverside to me, though.   Davey Jordan drove Wexler's Ferrari 275 LM at this event.

He also drove the car to 4th place at the Stardust Grand Prix in Las Vegas Nevada, on November 14, 1965 (No number listed).  I never saw the Stardust course so I can't say if this was it.

If anyone can ID the date and venue:  Please email me!