Little tidbit, if we are talking about Southern Democrats who voted for Reagan (and possibly Republican after that), they absolutely did not defect until 1984. Jimmy Carter dominated the rural South in 1980 and only (barely) lost the Southern states that he did because Reagan won the more populated counties...
That's the point. These people were the real Reagan Democrats, and they aren't Democrats anymore.
If you're looking for a group of "Reagan Democrats" besides them, then best fitting candidate are middle class suburbanites who were buying into fears over crime and racial tensions. This group also voted for George HW Bush, but many did defect back to Clinton and have been swing to D-leaning voters since. And they also don't really exist anymore, since the crime issues today are NOTHING like in the 80s, and people in this group are exactly the type of swing voters who are likely to think Trump is an ignorant buffoon. It doesn't really matter who the Reagan Democrats were, they don't matter 32 years later.