The photo was not taken at Pikes Peak. It was taken at another Colorado Hill Climb, the Buffalo Bill Hil Climb:
Below is a very rare photo of a one-of-a-kind sports car, the Bob McClure Jaguar Special. A long-distance photo of it appears in the article posted by ColoradoAirCooled. This is what it looked like up close on the start line of the 1954 climb.
My understanding is that the body was started by master metalsmith Charlie Lyon, but finished by another body man when McClure didn't think Charlie was making fast enough progress on it. Very C-Type Jag-ish looking body, but seems to have been a complete custom creation.