Horace--you're probably right on the numbers that wore the Ivy League style. The '50s seem to be the time that the ivy league became The Ivy League, primarily differentiating themselves from the riff-raff of new unis popping up around the country (/exaggeration) by refusing to sacrifice academic standards in order to lure athletes (1945, first Ivy Group Agreement). This also seems to be why I was relegated to watching Crew and Squash instead of top notch football
Ivy League style pushing into Miles' closet, among others--yes, I agree, and much of the result can be seen in the thread I linked. Rockers and hep cats exaggerated cuts and colors, which is now a certain designer's preferred source of inspiration. When the look moved to England it was completely integrated by the youthful Mod movement--GS probably has pics, I'll try to get a screenshot from Blow-Up. By then the worn-in, shabby quality was dropped and there was enough of a change to give the look a new name.
The Seeley G. Mudd library at Princeton has a phenomenal collection of historical photographs. I'll see if I can post any from the '30s-'60s. Looking forward to your thoughts on the "whys" when you have a chance.