https://www.nytimes.com/packages/html/books/phillips-souther...
(Similarly, I think you've collapsed the GOP of the 60s too far down; the Rockefeller Republicans were, on domestic policy, square in the middle of where the mainstream Democratic party is today. George Romney would have opposed AOC, but so does Gina Raimondo.)
At any rate, when people debate which is the "racist" party, they almost invariably ignore the fact that the US was a 4-party polity in the mid-century, not a 2-party polity. What's changed since then is that we have, from 1980 through today, sorted down to 2.