I can only help you with Mississippi. Here as long as you stay off the Natchez Trace you're ok. It's perfectly legal to have a loaded firearm concealed in full or in part or just flat out in the open in your vehicle. And just to add some meat to my statement I've been pulled over before with one visible, the officerwould see it, and ask that I unload it then continue with business. I've also had my vehicle searched on Highway 82 near Starkvillebefore (long story) and out of courtesy I told the Trooper there was a loaded gun and where it was and he mumbled "nothin' wrong with that" and just pulled it out, unloaded it, and put the clip in his pocket and the actual pistol in his car. But supposedly any firearm in any form isn't allowed on the Natchez Trace Parkway and you can be fined and they'll confiscate it. I don't know if you'd be arrested or not, though.

You might want to try packing.org i think it is. They have a page showing what states think of other state's CCP laws but I don't know if that'll help.