Ben Ettinger answers my questions about Hakujaden's aspect rato. It is indeed 4:3.
Hakujaden's aspect ratio is referred to as "standard", which I assume to mean 4:3, in all sources I've found. Shonen Sarutobi Sasuke was Toei Doga's first widescreen picture.
This should put the matter to rest. Enjoy some more screenshots from this magnificent movie. I've already watched this movie several times. I'd definitely stay up late and watch tonight if I wasn't so tired. This is a film you want to study, to understand. Hakujaden is a work of great skill and dedication, a landmark in the truest sense. And it deserves to be studied by animation and movie lovers the world over.