I have heard of double and tripled headed steam, but never a K4 and 2 E7s. I thought by the time E7s were the mainstay on the Blue Ribbon Fleet that the Centipedes and F3s were handling the helper job.
As near as I can tell, the 6000 HP Centipedes (BP60) appeared on the property in 1947, slated for front line passenger service. The first 2000 HP E7's (EP20) showed up in 1946 with the last batch delivered in 1949. Both locomotive types would have beem contemporaries in the late 1940's and would have shared the same assignments. The BP60's ran into trouble very early in their careers (1949-1950?) and were reassigned to express mail service. The helpers in the post war period were steam. The Pennsy had purchased or built so many steamers that it was quite a while before diesels were needed to take over the "snapper" assignments.
The centipedes were "detuned" to 5000 HP (their troublesome turbochargers were removed) and placed in helper service (BH50) in 1952.
