PC Through Freight Schedules Supplement 6-1-1972 – this is a supplement, so it is not complete. But it helps track changes to some schedules between the full schedules that are currently available.
Multimodalways.org has a 1968 freight schematic and 1969 and 1974 freight schedules available, along with many other documents. (Scroll down the page to near the bottom.)
Canada Southern also has the 1974 freight schedule available.