It's not necessary to bump topics and it's generally frowned upon by the moderators. Given that most people have other things to do besides hang out in the forums to answer your questions, you'll not always receive an answer right away. It could also be that people are researching your question, or it's the time of day and many people who might be familiar with your topic are actually sleeping.
As others have said, I can't think of any routes that this will run on that match your strict requirements. You can though run the consist on any route, and I highly recommend Neil Smith's UMR2025. While this route represents the Great Lakes region in Canada, the New York Central used to run along the southern edge of the same lakes and the countryside is similar. With the long fast runs, this is perfect for the 20th Century Limited.
For a US route, while not 100% accurate, there's an Ohio route that has similar terrain to what the 20th Century Limited ran on and actually represents a portion of the old NYC and this is possibly part of the route that the train ran on.
<kuid2:203554:100558:9> TRS19 - NS Sandusky District - Stage 2 - Route
<kuid2:203554:100798:4> TRS19 - NS Sandusky District - Stage 2 - Basic Session
If you're not satisfied with this route, there's always the alternative. There's something called TransDEM, a highly recommended third-party program that will allow you to bring in the actual terrain from the area where the train ran into Trainz, and then of course there's Surveyor. Whether you use Classic or S2.0, it's up to you, but plan on a very long slog of research and route building to create a route that's up to par as you take this terrain and lay your track accurately and place the trees, buildings, and roads as they are laid out on your map.