For anyone who is into modern freight cars, and is also on Facebook, I came across a group a while back called “Freight Car Enthusiast” that has been a big help with prototype research. I don’t think they limit themselves to a certain era, but most of the photos posted are cars built from the 70’s and up. Just wanted to pass it along.
Burl & others,
Another source of information for prototypes is the Yahoo group “Modern Freight Car List” for post steam era, and a " Steam Era Frieght Car List" for cars during the steam area. Lots of prototype information in all the various threads.
Also on Facebook is “Freight Car Photos,” and “The Magic of Freight Car Modeling and Weathering.” All are closed groups, you have to ask to join.