I imagine you would have actually gotten a pretty similar county split to Reagan/Carter in 1980, as uncomfortable as that is for the "Dixiecrats were the first to switch to the GOP" narrative.
There would have been some major differences as compared to 1980. Nixon would have done way better with black voters than Reagan and much worse with Deep South whites, even compared to Carter's very decent showing with that group. Nixon also would have done a lot better than Reagan in New England.
My point is that Reagan did not win the Southern states that he won in 1980 by winning the areas that had supported Wallace in 1968. He won those states by thin margins due to suburban strength, and he lost most of the counties that the eloquent users of Atlas would now classify as filled with "racist hicks" - voters that went to Carter, per county results.
Suburban Nixon voters in these states were probably just as racist, and Carter's win in the South in 1976 and narrow loss in 1980 was just an exception that proved the rule. It doesn't somehow mean that the nation
wasn't well on its way to an urban/rural re-alignment driven largely by race. It just means that, in two elections where race wasn't a big issue, the last vestiges of the Democratic Party in these states were just strong enough to favor good 'ol boy Jimmy Carter (himself far from racist) over Northern moderate Gerald Ford and Hollywood actor Ronald Reagan. But that was cultural, not racial. And it would change by the next election and never let up. So I really don't get your point at all.
"The narrative" is not somehow refuted by Jimmy Carter's performance in rural Southern counties in 1976/1980, nor would it have been refuted by Wallace winning those same counties in 1972. All that you have pointed out is more evidence of the slow but steady party re-alignment that was well underway by this point. Suburban voters in Mississippi hypothetically preferring the slightly less racist Republican Richard Nixon while rural voters hypothetically preferred the more explicitly racist Dixiecrat George Wallace would not somehow mean the realignment wasn't happening or that race had nothing to do with it. Party re-alignments are typically slow processes that take decades to fully take shape, and this one started as far back as 1944 at least, when FDR started bleeding some support to Dixiecrat electors.
Also, for the record, Goldwater (who Reagan supported) won every single county in Mississippi, and he did best among rural counties. And even if it were true that those rural counties were the last to flip solidly Republican, all that would mean is that generations of heavily entrenched Democratic support were hard to shake off completely. It doesn't at all refute the overall "narrative" of the South as a whole flocking to the GOP at the precise moment the Democratic Party abandoned the racism of the Dixiecrats while the GOP dogwhistled to them. It doesn't at all mean that was somehow a coincidence.
