The 86 and 82 probably have the most activity between the two. Try calling for Joe, N5OZG, on the 82 machine. He's the owner and monitors most of the time.
If you'll be heading up I-55 north, there's the 147.000 (-) 107.2 machine in Hammond. Make sure you put in a negative offset, most radios automatically want to put in a positive offset. With an HT on a magnet mount antenna, you should be able to hit that machine somewhere between Ruddock and Manchac. This is a little north of where you exit I-10 onto I-55 north. If you start to lose this repeater close to the state line, try calling for WB5ERM, Pete. He has a link/remote receiver further north. Basically, it's on the same frequency, 147.000 but this time with a positive offset. I am not sure of the tone though. That's why I suggest you try calling him on the air. He usually will answer. If you tell him I sent you, he will likely have some nice sarcastic things to say about me, ha ha. He's a nice guy though, we just rib each other a lot.
I go up to McComb, MS at least once a year to help with a public service event. Honestly though, we use the 147.000 machine and a simplex frequency. So I can't really help you out with freqs. in that area. The closer you get to Jackson, I would try the Jackson Amateur Radio Club repeaters:
Jackson Amateur Radio Club
Hope this helped you some. Have a safe trip.
73
Scott
KD5PCK