Just read your axle thread, looks like we are on similar paths. Looking at your profile looks like you are near me also I live in grass valley near Rollins lake.
I have never heard anyone say they wish their axle was skinnier, especially under a top heavy fj60
Mine won't be narrower as is. They'll be the same as the fzj80 rear with spacers up front which is still wider than oem fj60.