Frankly, it depended on the route of the cars for ease of switching enroute. There may also be two dining cars in a train, one for coach and one for first class. A good, generic train might look like this:
Locomotive
Baggage-Express
Baggage-Mail
Express Reefer or Boxcar
Coach
Coach
Coach
Dining Car
12/1 sleeper
12/1 sleeper
10-1-2 or 8-1-2 sleeper
Dining Car
10-1-2 or 8-1-2 sleeper
Observation or buffet lounge
Railroad timetables for your railroad of choice will describe what accommodations were used for each train for a given year (and/or season). Some railroads liked the 12/1, while others preferred more 8-1-2 or 10-1-2 (even some 6-6 or 6-3) sleepers.
Look at this schedule for the Tamiami Champion (ACL) for 1941:
http://www.streamlinerschedule...hampionec194106.html
From New York to Miami the train consist kept changing, switching out cars all along the route. Other railroads and trains were similar in nature.
Hope this helps -