I can't remember the year thing. I want to say that only 79 got the granny first model......or maybe 79 was the one that got the close ratio.....I don't know. Just make sure you get a T18a from a CJ.
Sully, I'm just guessing here, but it seems like you go on alot of long distance wheeling trips in your Jeep, so overdrive would be a nice thing to have. I feel funny about even getting close to recommending a T5, but I think a granny geared transmission is a choice that should be heavily weighed before jumping on it. It's the best thing since sliced bread to some people. Do you know anyone that has one that will let you spend some time behind the wheel? I mean, if rockcrawling is your thing and you can live without the overdrive, then it might be for you. You can always play with the gearing in other areas to compensate. With the granny 1st and loss of overdrive, you might be better off swapping to more highway friendly diff gearing and then gearing down the tcase for offroad.