If making money is involved, I would say you are not overthinking it at all and it would be worth your time and money to consult a copyright attorney about what would constitute fair use or if the work would be in the public domain.
It sounds like the system is a mess regarding orphan works, assuming this report is up to date.
https://www.copyright.gov/orphan/
Yep, still a mess in the US
https://abj.artrepreneur.com/using-orphan-work/
Given the year of publication, without a copyright renewal I think the work is in the public domain. It sounds like the renewal would have had to be in the 28th year, so 1974, with the Library of Congress
https://onlinebooks.library.upenn.edu/renewals.html
Again, I probably have not told you anything you don't already know, and I could be wrong on all counts; but I can feel good pretending to have been helpful.