rear stopped in something like 67 fronts were course with fine spline inner shafts til ~75
Clarification: In 6709 birfields were introduced to the front, replacing the earlier design ball and claw joint. As Wes pointed out, they had coarse inner for the differential side gears and fine outer splines for the birfields, however the outer birfield stub were coarse spline with 6 splines for the drive flange or locking hub. In 7509 disk brakes were introduced to the USA market, and with them came fine (27) spline outer birfield stubs. Other markets outside the USA did not immediately get disk fronts, but they did get the newer, fine splined birfield. The birfield was changed starting in 7901 and was made shorter: this was the birfield design used for all cruisers, mini trucks and 60s until the end of FJ62 production. This shorter birfield can not work with 7509-7812 hubs with the circlip, and instead a large fender washer is used with an M8x1.25 bolt (or marfield tack) to hold it on.
The birfield joint was originally manufactured in Germany at the Birfield factory, and was invented by a fellow named Alfred H. Rzeppa in 1920. From:
http://www.freepatentsonline.com/6908231.html
"21. The shapes, and the like, of the constituent parts of the constant velocity joint 2 are the same as those of a known constant velocity joint of a Rzeppa type or a Birfield type."