You are asking a tough question. You might try the PRRT&S (Pennsylvania RR Techincal and historical society).
I understand that MP54 or mp54 ( I did not think there is/was a difference) were the powered versions of the cars. The P54 or p54 was the unpowered ones. The original cars were built as P54s but with the capability for eventual conversion to electrial powered cars.
There were unpowered trailers used in the commuter service. I do not know if these had pantagraphs or not.
As for pulled by locos, there have been notes of P54 s being used in commuter service around Pittsburgh, where there is no overhead electric. There was a note on "what happened on this day when - -" historical site for the PRR that listed the last run of P54s on Pittsburgh commuters and the date as I remember was in the mid 50s. I don't know if they were also used around Chicago by loco pulled trains.
I have no ideas or knowledge about their use with heavier cars and how.
