I saw a listing on the above vendor's site for "JETAWAY Rebuild Overhaul Manual 1956-1964" and thinking this was some wisdom concerning overhaul tips and tricks, for $38, I ordered it (shipping was another $12.99, which should not be; this could easily ship via media mail as bound printed matter). I should have asked some questions first (and that part is on me).
The first leaf (printed both sides) of the spiral bound "book" consists of exploded diagrams of the major assemblies. The next leaf (again, printed both sides) consists of their part numbers and applications for various components. The remainder of the "book" (54 pages) is simply a reprint of chapter 6 (Hydra-Matic Transmission) of the '63 Cadillac shop manual (which I happen to have on my shelf). Ugh. I'm such a trusting fool. Never judge a book by its cover, and that's what I saw: a nice color cover (that, and a description).
There were two inside page previews available on the site, but for some reason, I never put the small images (and yes, they're clickable to expand the view) together with content with which I was/am already familiar. Again, that's on me.
Still, $38 + $12.99 shipping (it was packed well, in a box, inside a ziploc bag taped to one of the sides) is a lot of money for 54 pages from a shop manual which is readily available online. They did ship quickly, too.
I have not complained to them because as I say, I should have looked more closely and asked questions if I wasn't sure. I take full responsibility for that. As to the rest of their information or rebuild kits, I could not say.
https://www.classictransmissionsolutions.com
Just some thoughts to keep handy if anyone else is looking for that one nugget of valuable information. Caveat emptor.