I guess you mean
The Museum of Railroad Timetables not the RPA? The museum ends with January 2016. I don't know how far you are going back with buses, since at some point it's interleaved with changing train service. For what it's worth, Suffolk VA was a Thruway stop in the 1970s, then it was dropped. The NFK-PTB train returned in 2012, but the Suffolk station was, and is, skipped.
By contrast, Amtrak's May 1975 map and schedule had Southern Railway's Crescent, so it had the Asheville NC branch and its 14 stations. Those never became a bus in the schedule. The 1975 schedule really shows a different world, with a full page promotion "Amtrak and Greyhound - a Good Connection," and the Florida car rental deals. Then plastered on the Asheville branch schedule is "(finger icon) Notice! Application has been made to the appropriate regulatory body to discontinue Trains Nos. 3-4. Consult agent before travelling."
The October 1, 1979 schedule has a Thruway to Key West FL.