Assuming your '79 is a 4WD...
It would be the same t-case that came on your '79 as far as how it fits. There is a difference in how the input shaft is shaped. The '79-'80 has splines all the way and the '81+ has a "fuse" where it necks down so it is a little weaker. Not a big deal unless you are making a huge crawler out of it.
