Found some much clearer old pictures of the pass. It's a collection of what are called postcards, though some just look like old photos here:
http://www.66postcards.com/postcards/ca/index13.html . That link starts at the summit, but the index pages are ordered to mostly track route 66 from end to end, so it includes old pictures of Barstow and San Bernardino.
Meekers:



This one is labelled "Blue Cut". I had a hard time pinning down this one until I noticed the water tower on the left and it dawned on me! I recalled passing an old dilapidated water tower in that group of buildings off old route 66. It's the same one! It was also an old 76 station sign.
Google street view of the location in 2008 before they dismantled the top portion of the tower:
https://www.google.com/maps/@34.2571292,-117.4655887,3a,75y,336.76h,101.4t/data=!3m6!1e1!3m4!1saYRNPft9HtAvTiEg0lSlbA!2e0!7i3328!8i1664The photographer was standing on Applewhite Road. Keenbrook, I think this is called.

A bit further north of the previous photo, looking south at the "rest stop" area near Lost Lake Those look like maybe toll booths?

A view from across the wash on the train tracks side. This is between Keenbrook and the Blue Cut rest area looking north-ish. Only one set of train tracks at the time of the photo:

Later photo:

(out of order) One of the earlier alignments of 66 coming down from the top of the pass looking south:





The "big bend" coming down from near the top of the pass:

Back to Blue Cut, looking south

Blue cut, just north of the rest area, looking south

Monument at the end of the road past McDonald's, behind the scales:

Camp Cajon:



Same. Is that an apple truck I see? Or did all "tractor trailers" look like that back then?



