So I've been doing some digging on the narrow gauge pacifics that ran up in Newfoundland, and did find two basic arrangement drawings with the google search... But I'm curious as to whether there's any other more detailed drawings floating around out there, maybe in a book or something like that... I've attached what I found for reference.

That was everything I had on them ;)

I don't recall seeing much written about the Newfoundland Railway, other than a few websites. You could check out Don McQueen's series of books on Canadian National Steam Power, and there is a specific volume on (all of CNR's) Pacifics.

There is a facebookpage titled “Exploring the Newfoundland Railway” which you may want to try if you have not already.

And while not locomotive related, two of the Newfoundland Railway coaches are at the NJ Museum of Transportation/Pine Creek RR. One has been restored to operation and is used on a daily basis, riding on regauged trucks for 3’ operation. The other coach is in storage.

J.R.