(Note added on Thursday afternoon - you can ignore this post - it's got good info, but I was lead down the wrong path, due to not looking at the train first - I looked at the physical El construction - there's some interesting info here - but it's not really needed for identifying photo #3 - Gil)
Photo 3 - if one looks at this photo -
http://nycsubway.org/perl/show?53332 - these El structures look similar - smallish round vertical pillars and X-braced girders under the track structure.
That photo is of the infamous 110th Street curve on the 9th Avenue El - the first El built in NYC. It is in this article -
http://nycsubway.org/articles/rapidgreatcities.html
Here is an even better view of the El structure -
http://www.shorpy.com/node/8343?size=_original - compare the columns in this shot to the ones in photo #3 - I would say a match for the basic construction style.
This could be a shot of the Polo Grounds Shuttle that ran from 1940 (end of 9th Avenue El service) until 11:59pm on August 31st, 1958 !
That would allow that construction style to show up in a photo Hal took in 1955.
Maybe this is part of the leads to/from the 159th Street yard that the 9th Avenue El had - which would make this Manhattan - not the Bronx - and it might be the parts that were kept to support the Shuttle operation. Most of the yard was scrapped by 1946.
See
http://www.nycsubway.org/lines/9thave-el.html for some history. There is large Historical photo collection available for browsing.
Here is a rather large, annotated photo gallery of the 9th Avenue El -
http://picasaweb.google.com/MercuryWW/NYC9thAveEl.
Also check out -
http://cid-616b1f67315e9e01.office.live ... L9/Yard159 - just the 159th Street Yard Complex.
And if you click on the L9 at the top of that gallery, you will go up to yet another gallery covering the 9th Avenue El.
And, how about an early film - going around the high curve at 110th Street -
http://www.youtube.com/watch?v=x9XLGc7d0zA
And now for a little bad news - I can't find any other shots of that particular car type - now I haven't looked everywhere, and I haven't dug out my EL books - buried in the basement at the moment - put it looks a little strange - only 2-doors per car, inset from the ends, no provision in the floor beams for a third door, but the front looks like many other NYC El/Subway cars - so I'll keep looking.
Hope this helps, or leads you in a good direction.
Gil, known as Bill somedays ...