My best guess is that this photo was taken on the short straight leading to the hairpin although it could also be on what was known as the "hangar straight" where the infamous Webster Turns had been located.

The headlights are on so my guess is that Bob was behind the wheel when the shutter snapped.   The car alongside us (and passing) is the "Sebring Sprite" driven by "the girls", Janet Guthrie, Lianne Engman and Donna Mae Mims.    

Note the crumpled front fender on the PV.   This was from clipping a tire marker through the esses that followed the MG spectator bridge.

Those esses could be taken in a straight line if one just barley grazed the tire marker on the right.  A miscalulation of an inch or two and the lip of the fender caught the marker with the result you see here.

Photographer unknown