I'll only do Post WW2:
Most : 2004(Republicans Prior to 1992 were too strong in the Coasts for anything prior to that to be true, and same with Democrats Prior to 2000 in the South)
Least: 1976(GOP Strongest in the West and Weakest in the South)
I agree with this. Though of course, Bush in 2004 ran behind Trump's 2016 totals in Appalachia, and behind Trump throughout most of the Midwest. Arkansas was actually within single digits that year! 2004 was the last time that the Democrats were even remotely competitive in that state at the presidential level-it was also the last time that Democrats won a Senate race there against a Republican, as Blanche Lincoln was elected to her second and final term. She won by 12% while Bush carried the state by slightly under 10%. And Bush obviously did far better than Trump in places like Virginia, Nevada, Colorado, New Mexico, Texas, North Carolina, Arizona, Georgia, and Florida, all of which are now turning to the Democrats.
As for 1976, Ford's Western strength that year was very noticeable. The only Western state Carter carried was Hawaii, and he won it by less than three percentage points. 1976 was the only time from 1912-2012 that Nevada did not vote for the winner of the Electoral College, and was also the only time during that period that New Mexico did not vote for the winner of the popular vote.
