Half tons only. 3/4's and 1 tons got (in waaay old trucks, a la pre-'37) Eatons or (in later trucks, ie 73+) the 14 bolt.
Now, which years... I donno when it started. I know they were available for '73-74. The 12 bolt ended ca. 1980 with the advent of the 10 bolt rear.
-- A