I agree, it WOULD be neat to know, and I hope you find out. Of course, both PRR and NYC had dozens of E-8 units, and -- since sometimes the work needed on an engine doesn't take the same amount of time as the work needed on the rest of the locomotive -- I think they switched engines around from one locomotive to another in the course of repairs(*). So you might find out that "your" engine served in several E-units.
(*) I have read somewhere that, since the New York Central had a large nummber of RS-3 units, when one went into the shops for major work and had its engine removed for overhaul, it would be put back into service with the first available 12-244 engine, which in general wouldn't be the one just pulled from it. They only had a very small number of RS-11, however, so no "pool" of 12-251 engines. So, when an RS-11 went into the shops for similar work, it would (engine overhaul typically taking longer than repairs to the rest of the locomotive) just sit with an empty engine compartment until its original engine was ready to be re-installed. ... So, I have no idea HOW many engines have chugged away in a DeWitt Geep since Alco built it!