Eric,
From what I have learned in the research I've done for my layout, the Pennsy used every make of diesel built. In the 40's and 50's there were Alco PA's. RS-3's RS-1's and S models. They had E-7's and E-8's from Electro-Motive, Fairbanks-Morse Train Masters, C liners and Erie Builts. They purchased Baldwin road switchers, switchers, "centipedes" and "sharks". Even G.E. 44 ton switchers were on the roster.
They purchased these units the same way they purchased (or built) steam...by the hundreds. Altoona never built any diesels that I know of (I think Juniata shops closed down in 1946), but the purchasing department bought them from everybody.
In the early years of deiselization the PRR ran their units in strict consists (even classified them that way. They would run four F-7's and classify the whole string as one locomotive (EF-4 was A-B-B-A with about 4500 HP). They did this with all their road units. Two Baldwin centipedes were a BP-2 (A-A with 6000 HP). An Alco PA set was a AP-2 (A-B with 4000 HP or an AP-3 (A-B-A with 6000 HP). In the early 50's the operating department must have realized how flexible diesels can be. They started classifying diesels as single units by their manufacturer, assignment and horsepower. Those F units became class EF15. The PA's became class AP10. Only the centipedes remained a pair being class BP60 (eventually relegated to BF-50 and BH-50 after the turbos were removed). The more diesels that arrived on the property the more the units were used as needed. By the mid to late 50's it was not uncommon to see F units and Geeps or Alco A units with EMD B units on the same train.
The Pennsylvania standardized everything, but it was such a big road that it needed a variety of different locomotive types for different jobs and plenty of each type. It's one of the reasons I model the PRR.
The short answer is that it is prototypical to model the PRR with a mix of diesels.
Regards,
Frank Musick
