I have a question about the interior difference between the C&NW bi-level gallery cars used in suburban service in the Chicago area versus the bi-level gallery cars used in the "400" service.
C&NW Forever
I'm not sure about the coach-lounge, the parlor and the coach-parlor but the long-haul coaches (700-709) had 96 seats with no center-facing bench seats upstairs. They also had two restrooms, one at each car end. Luggage racks were located in the vestibule in the area where the outer parts of the stairs were located, with the doors only opening for the center of the stairs.
The 400 equipment actually predated the suburban cars in the use of head-end power. Suburban gallery coaches 1-17 were actually built for steam heat.
More information can be found in "The 400 Story".
From what I remember, and subject to correction:
1. The C&NW gallery long distance cars were built with the idea of possible conversion to commuter cars. They never were converted.
2. The parlor was similar to the coaches, but with single seats both sides upstairs and downstairs.
3. The diner was not double-decked in any way, just a single-level car with some kind of lightweight top to match the gallery cars. I'm not sure this lasted for the duration of the operation.
4. At least some of the cars did make it into Amtrak service before retirement.
I rode the train once. Flew from Boston to Midway, Chicago, taxi to Roosevelt Road, Electroliner to Milwaukee, taxi or trolleybus to C&NW station, and 400 to De Pere. Had dinner on board.
Other material is from memories of rreading TRAINS.
The dining cars and the baggage-tavern-lounge cars were rebuilt with HEP and other modifications and were fitted with false high roofs to match the bi-levels. Shortly after the Amtrak start-up, I recall seeing one of the dining cars at Hyman-Michaels scrap yard in Hegewisch.
Two of the specialized bi-levels were rebuilt to "Sip'n'Snack" cars around 1968 or 1969. The third was rebuilt to a suburban coach. The straight coaches plus the "Sip-n-Snack" cars were eventually picked up by Amtrak and numbered in the 9600 series. They served on various short hauls out of Chicago (Illinois Zephyr, Illini, and others) before finishing out their days on the Valparaiso suburban locals.
In the interests of full disclosure, my first long-haul passenger train ride was on the Peninsula 400 from Chicago to Marinette around 1965 and I have been fascinated by the long-haul bi-levels ever since.