Are you saying that many Southern Democrats did not switch to the GOP after the passing of the Civil Rights Act?
"By 1962, the Republicans were pretty routinely winning Southern states in Presidential elections, and there were twelve Republicans from the South: two in Texas, two in Virginia, four in Tennessee, two in North Carolina, and two in Florida. But that doesn't explain the "redness" of many of the Southern districts. At this point, a near-majority of Southern Democrats had voting records that placed them on the right side of the ideological spectrum, even excluding civil rights votes."
In other words, by 1964, most Democrats were already voting like Republicans on non-racial issues. On a blank slate, these Democrats would be Republicans; they were true DINOs. But three things kept these Democrats from actually calling themselves Republicans: Jim Crow, seniority and Herbert Hoover.
This is why we see such little change from the general trend post-1964, even with the end of Jim Crow's strange career. Republicans picked up a few Congressional seats. J. Strom Thurmond became a Republican, and a few other prominent Democrats followed suit. But the Southern Congressional delegations continued to be dominated by Democrats. Almost all of the signatories to the Southern Manifesto remained Democrats until they left Congress. Some, like Russell Long and John Stennis served as Democrats into the 1980s. When Haley Barbour ran against Stennis in 1982, he lost by a nearly 2:1 margin. George Wallace was elected Governor of Alabama as a Democrat in 1982."