Woodies or Steelies?

[doctorwayne]

Santa Fe started re-building their wooden reefers, like this one...



...into steel cars, like this one...



...in the late '30s, but were still doing so into the '50s.

50' wooden boxcars, usually single sheathed, became quite prominent in the '20s, with steel versions appearing more commonly in the mid-to-late '30s.

Santa Fe's Bx-3 and Bx-6 boxcars, along with their 50' Fe-Rs, built in the early '20s, lasted into the '50s, albeit sometimes modified or in other than the original service for which they were designed.  I'm planning on scratchbuilding several of them, as they'll fit well into my late '30s-era layout.

Steel gondolas and flat cars, in both 40'/41'6" and 50'/52' versions became common in the late '30s but appeared earlier, and by the '50s were predominant.  There were still a lot of 40' and 50' composite gondolas around in the 50's.    
Walthers...



....and Intermountain both offered nicely-done versions...



Another thing to keep in mind is the wide variety of house-car heights still in use in the '50s, from the 8'6" inside height of  Pennsy's X-29s...

 

...and  Central's USRA-designed steel box and automobile cars...



...to the 10'6" inside height of the 1937 AAR cars, most of which were built in the late '40s and into the '50s...



Train Miniature covers the lower-height cars quite well, both wood (single- or double-sheathed) and steel, and they can be made into decent models or used as-is.  They're widely available at train shows and on the re-sale market on-line, while Intermountain/Red Caboose offer more accurate versions of the steel cars.
For the taller 40'ers, the Athearn Blue Box car is a reasonable starting point, as are those from Accurail, Intermountain, and likely many others. 
Bowser offers some nice steel boxcars, both AAR and Pennsy-style suitable to your layout, too, while Accurail is an affordable choice for the higher 40' wooden cars, both single and double sheathed...





...and the 40' AAR steel car...



Wayne