Looking for references

I'm looking for some references on the hows and whys of car maintenance on the D&RGW narrow gauge. As I get more involved on my pet project (the 0579), I'm starting to get interested on how all cars where built and maintained. I've got some of the Narrow Gauge Pictorial series, but they concentrate more on photos, not descriptive text.
Ideally, there'd be something out there similar to the Norwood books, but I don't recall ever seeing what I'm looking for.
For instance the types of questions I'm looking for is, how much did the brake systems change over the years?; why were caboose trucks constructed in the manner that the current 0578 trucks exist? etc and so on.