The front 80 third is completely different and won't bolt up.
The rear depends on the year of 80. FJ80 had semi-float rear, the later FZJ80 was full-float. From what I understand, the full-float will work in the front of a 60-series, but requires different inner shafts (something about the splines, I think). No idea whether that means you can use the semi-float without mods.
aren't 60 and 62 thirds interchangeable front and rear? so if it'd work at all it'd work for both fr and rr?
The 80 series diffs are 4.11's with the same flange pattern as the late 60/62. The thirds bolt right into the housings. If you are installing an 80 diff into a SF 60 housing, make sure to get the SF 80 diff as it will come with the spacer block installed.
I have an 80 diff in the rear of my cruiser.