I'm working on the core of a 36'4" car right now. Probably stuff you already know, but the GN reefers show up in numerous yard photos on Shorpy in Duluth and in the City of Vancouver archives. The one on page 96 of the Rusty Dusty is a 38'1" car and the one on page 119 is of the smaller 36'4" class built in '02. You can find decent outside dimensions in the 1905 ORER that is available online.
I know there is at least one photo in Leavenworth: A pictorial History of a car but I can't make out the number - it's 5 digits. I'm pretty sure they show up in some of the Leavenworth and Cascade Tunnel Station shots out of Bob Kelly's (Skykomish Historical Society) Monitor to Monroe Depot CD and the electric loco CD.
I don't have a 1927 freight car diagram book but I do have a 1950 MOW book with one of the 38' 8" reefers converted to outfit. It doesn't say who it is made by but it does say that the trucks are Haskell & Barker. They're 5'2" WB on 28'8" centres. I notice that the ends overhang 6' (12" more than similar sized H&B boxcars). 5'2" WB (40T?) trucks show up often on the GN's H&B built boxcars of the era. There are some ex-URT reefers in the MOW book as well that the GN picked up in 1920 - I don't know anything about their history.
Until I get my hands on an early diagram book my 36footer will ride on 30t diamond arch bars and have four trussrods like the one in The Rusty Dusty.
If you want the MOW diagram email me or use the private message thingy.