That would indeed work, except that most, if not all, the remaining steel cars now have painted interiors; the original faux wood grain finish is long gone. That need not be a problem, as the porter's job was essentially unchanged through both periods, just explain the different era when moving between cars. Use the highly ornate berths in a restored private car to show the operation of the berths and give some idea of the opulence of these cars, and use one of the steel cars to show the details of the smoking and wash rooms, explain the details of the porter's routine, and show his normal rest station on the smoking room couch.