A classic publication that was hugely influential back in the day was The Model Railroader Cyclopedia. The classic version of this was published in one volume and was a very important, standard resource in those pre-internet days.

My copy is the 1944 version (copyrighted 1943), the fifth edition. Using that copyright page as my source, the previous editions were published in 1936, 1937, 1938, and 1940. Judging from searches I believe the version I have might be the most common, which makes some sense as by that year of WWII model railroad supplies were really short, but you could buy a book like this one and dream about what models you might build after the war.

The book contains several short and helpful articles, and pages and pages of scale drawings, many folding out from the book. Many of these if not most were published previously in Model Railroader, but I don’t think they all were.

It is a fascinating book to just look at periodically, you can tell that many of the models featured were actually produced for the hobby market. Then you have the question, which came first, the models or the drawings? I’m inclined to think the drawings, although who knows, maybe there was some coordination with manufacturers involved, and the drawings were produced for the manufacturers and then published.

In any case, the resource has come up in this site several times for models that were built from the plans in this book, including a drovers caboose, the Scale-Craft 4-6-2 and 4-6-4t, and the Graceline quad hopper and utility flat. 

The Cyclopedia is pretty available (eBay, etc.), if you don’t have one I think this is one that anyone interested in older scale model trains really should pick up as a reference.