DEHUSMAN The NYC and other lines published the train consist and amenities offered in both their public timetables and official guide. Here's an example from the Century's great rival (I'm a DPF - Drooling Pennsy Freak) https://everipedia-storage.s3-accelerate.amazonaws.com/NewlinkFiles/1331476/5850598.jpg. So you'd better offer the same accomodations in each section or the Cusomers (who are paying extra fare for those accomodations) Will Not Be Happy. Unhappy customers ride other railroads.
Also, I remember the "Boston Section" of the Century being The New England States (Boston - Chicago via the B&A and NYC)
"The New York Central introduced the New England States on June 15, 1938, coinciding with the relaunch of the Twentieth Century Limited. The New England States was an all-Pullman train which ran from Chicago to Boston via Toledo and Albany. With the launch of the New England States the Twentieth Century Limited ceased carrying sleepers for Boston."
https://www.american-rails.com/nw-engld-sts.html