Pennsy had only 5 streamlined steamers - one full streamliner, and 4 with less shrouding. However, they had a bunch of name trains that were streamlined starting the late 1930s. Steamers had to be serviced, lubed, and whatnot after each trip, so they often did not return on the revrse of the same train. So just given the numbers, lots of unstreamlined steamers would have pulled Pennsy passenger trains from the Late 1930s into the diesel era. Pennsy did not start getting passenger diesels until the late 1940s and still ran steam to the mid 50s. The T1 4-4-4-4 did not even enter service until the mid - 1940s and served pretty much exclusively as passenger engines. this was Pennsy's version of a modern 4-8-4.
An interesting one was the reading crusader. It did have at least one streamlined steamer. I don't know if it ever ran with unstreamlined ones, but I would guess it did. However, to save time at end terminals, they had 2 round end observation cars built for it. It had one on each end, so it did not have to be turned to have one at the back. the tender of the streamlined steamer had the back end built with an overhang to blend over the streamlined observation car.
