I would start with a Wheels of Train car vs. the MT 60' mail car, in as much because you have a good bit of windowless sides that you likely would want to keep. And you have to remember, though, that the 6 cars had separate origins, and this could and should be taken into consideration.
GN 1 and 2, built by St. Louis Car Co., had one large door on one side only with two windows on the opposite side, while 3 and 4, also St. Louis built, had small doors on both sides roughly placed over the left truck on both sides. GN 2 sold to Western Pacific, date unknown. GN 3 sold to AutoTrain.
GN 5, rebuilt from GN diner 1001, had a similar door and window arrangement as 1 and 2, but when created in the GN shops this car came out with a streamlined roof, matching the profile of new lightweight equipment. both cars was sold to the Spokane Portland & Seattle in 1969 to allow for freight locomotives to be used on all four of their trains, though passenger cab units remained in service.
GN 6 and 7 were built the cars rebuilt from the short mail cars and featured a single center large door with a single window opposite the door on the other. GN 6 was sold to the Western Pacific, date unknown.
GN 8 and 9 were rebuilt from boxcars.
Photos of these cars can be found at the
Passenger Car Photo Index under AutoTrain, GN and WP listings and if you are interested I do have diagrams that I can share, if you would be interested in seeing them. Email or PM me and I will see what I can do about sending them to you.
