I've looked into it with a few of my 80-96's but never gone further than that because the trucks always got stolen or fell thru the ice & disappeared or something like that.
You'll need more than just the axle. If you can get a parts truck that would be the way to go. You'll need the whole coils spring setup, meaning the upper coil mounts as well as the cups & all for the axle. Having the 78/79 radius arm brackets would help but I'm sure you could modify the existing mounts (replacing what you have w/78/79 mounts will also give you the opportunity to drop the bracket so you're not stuck using offset C-bushings because they're really only a partial fix). You'll have to fab a trac-rod mount so getting the one from the 78 will help because at least you can modify it and not have to start from scratch.
Once you have the coils mounted, a track-rod bracket & the radium arms brackets where they need to be you can pretty much slide it under. Not having a 78/79 in the yard to look at I forget what steering mods need to be made but it's nothing crazy.