Nice shots there. Man I miss the 70's. To me, THAT was my transition era.
Sure was. I wasn't there to see it myself unfortunately, but you still had first generation getting replaced by second-gen.
40' boxcars getting replaced by the modern Railbox style welded, exterior-post cars. Similar stories with other car types. (Railgon, then-modern 89' TOFC, etc.)
Beginnings of the major railroad mergers and consolidations (BN, PC, CR, etc.)
Major image updates on other railroads (particular on the two main Canadian roads - CN in the early 1960s, CP in the late 1960s with transition through the 70s).