Stay on 20 through Meridian into Alabama. Then take exit 1 in Alabama. Hang a right at the top of the ramp to cut over to 80. A little quicker than getting 80 in Meridian.
You'll have a little bit of two lane until about Demopolis, then a tiny bit more before you get to Uniontown. Make no plans to stop in Uniontown.
In Selma, take truck 80 to go around the east side of Selma instead of through downtown.