I actually just cut up my fj80 rear this weekend to make mine wider for a t100 build but i can confirm the axle lengths i measured were:
long side: 36-7/16"
short side: 28-15/16"
this is from inside mounting face on axle shaft to end of splined section.
WMS to WMS is exactly 63"
if you cut the spindle off at the weld with a cutting wheel like i did you can reuse the spindle. you will need to machine the ID of the axle tube or the spindle to get a press fit though.
here is a picture of the spindle i cut off and the axle housing i cut it off of.
if you want any more measurements while i have it apart let me know.
