I will start with the blunt statement that if you want a model of the Alabama that's at all accurate, do not buy this kit. Just for starters, the masts are not raked as they were on the real ship, which ends the conversation as far as I am concerned if built out of the box or even modified in deck detail. It's a doable modification, involving replacing the masts, and I have no idea what then happens to the topmasts. And so on.
But the story gets a little interesting. The Alabama is indeed a revised Kearsarge, as Tilley notes, however it's a very good basis for a Kearsarge from 1864. The Kearsarge kit, on the other hand, is based on her post 1888 refit. I won't repeat the details as they are easy to find online, but check some of the respected other ship model forums and you'll see.
One niggle either way is that the gun swivel tracks on the K kit are correct for that ship, the ones on the A are not for that ship, but they also are not correct for the proposed refit as K i.e they are not the same as the K kit. Revell simply made them up.
If memory serves, and it doesn't always, there's a set pending from one of the good US model makers of mixed media kits.
There's always a good benefit in bidding on those older kits if you like good box art and that old kit smell. I have an original of the Cutter Campbell, for which I paid a lot more money than the rebox/ rerelease, but it's a neat thing to get out and look at.
I'll wager a glass of rum that at the end of the day the old box costs much more than the RoG kit.