Apologies for taking so long in responding! I can add a few details to Lv325's answers.
(i) According to Rehor's book, "The Nickel Plate Story," the 11 PA-1 units were built in 1947-1948. The one photo of a PA-1 in the book, taken early in the units' history, shows an unmangled nose. Not sure whether the book says explicitly that the 11 were traded in on 11 Alco roadswitchers (I basically looked at the motive power appendix and didn't re-read the whole book), but the last 11 1800 hp Alcos -- some of which had steam generators for emergency use on passenger trains -- were built in 1962, and the numerical coincidence (11 of each) strongly suggests a trade-in deal. Rehor gives the Alco model of these roadswitchers as "Dl-701-XAP"; I have been told by someone (on some Internet forum or other) that the XAP suffix denotes units built with re-used parts from trade-ins.
(ii) Jim Boyd's "Passenger Alcos" gives some further details. (a) the bell-in-the-notch modification was made starting in 1959 (about the same time that, with the declining number of NYCStL passenger trains, the PA-1 started getting used on freight). Motivation was that, in their original (below the frame) location, the bells tended to get clogged with packed snow. (Recall where the Nickel Plate main line is relative to Lake Erie: "Lake effect" snow would be a constant operational nuisance for the NYCStL!) (b) the PA-1 were traded in for the roadswitchers: all officially traded in at once, but a few then rented back from Also while the replacement units were built a few at a time. (So NYCStL was never down by the full 11 units as the replacements were built.) (c) Unlike previous 1800 hp Alcos on the Nickel Plate, these were not RS-11, but RA-36. (Slightly upgraded model, sharing a new control system -- "transistor throttle" -- and a few visible carbody modifications with the 2000 hp RS-32.)
(iii) An "Extra 2200 South" article (issue #76) on the RS-32 and RS-36 notes that these NYCStL roadswitchers were built using the General Electric GT-566 main generators from the PA-1 units. (Buy an RS-32 or RS-36 with no trade-in and the standard equipment would have been a GT-581, but many -- I think a majority -- of the units actually built of these models had GT-564 or GT-566 generators from first-generation Alco trade-ins.)
(iv) Lvrr325 mentions one unit going to the Wabash. As Boyd tells the story, the Wabash was planning to rebuild one of their own PA locomotives after a wreck, and bought the ex-NYCStL unit as a source for parts. (Officially, therefore, not a wreck replacement, but of course in reality the line is a bit fuzzy: the rebuilt unit would have been a hybrid. Cf. the British destroyer HMS Zubian.) In the end the rebuilding was not done; the unit was scrapped after Nickel Plate and Wabash were merged into the N&W.
Again, sorry for not replying several weeks ago to your question, Statkowski.