K-37 Technical Questions

I know, what's an EBT guy doing asking questions about a D&RGW loco... Well, I'm writing a review of Accucraft's 1:20.3 model of the K-37, and I want to make sure I have my facts straight.
Anyway, when these locos were rebuilt from the C-41 locos, how much was retained? From what I've read, the boiler was used, but how much else? Cab? Domes? What about the tender? Did they reuse the frame and tank, or just the trucks (or were the trucks merely spares lying around the shops?)
Also, there's a metal bin/box "thing" on the fireman's side of the smokebox that appears in some photos. What was this used for?
Does anyone know of published plans for the K-36 (for size comparison?)
Thanks much for your help.
Later,
K