slant 6 auto(904) to 4 speed help

Taken from slantsix.org/articles
There were three different sizes on production four speeds. There was the 5.125" dia. IBR used on the 1975 and later Overdrive units, the 4.80" dia IBR used on "Hemi" transmissions, and a 4.35" dia. IBR used on everything else.

833OD - 1975 thru 1987 Overdrive 3.09:1 - 1.67:1 - 1:1 - 0.73:1
833 4speed - has a 1.1 final ratio.

With that in mind, I'd say that if the IBR diameter is 5.125" then it's a OD unit but if someone can decode the casting number that would be definitive. May want to post in the 4-speed forum with the number....not too many of us frequent the /6 discussions :)