Re: Scratchbuilding HOn3 or On3 chassis.

Here's the list of installments and what each one covers:

October, 1982: A USRA Mikado in brass - overview, tools
November, 1982: 2. Frame and drivers
January 1983: 3. Bearings, gearbox, drive train, cylinders
March 1983: 4. Engine trucks and coupler
May 1983: 5. Boiler and cab
July 1983: 6. Boiler details
September 1983: 7. Valve gear and rods
November 1983: 8. Tender construction and painting

That October 1982 article would be all you need to figure out how you'd want to go about this. I just looked at the Kalmbach site and they don't have that one; I found a 1967 issue I was wanting on ebay...