I been running a Sagainaw 4 speed with an OD for a few years now,I did the build,farly easy.Ya need the OD unit from a Saginaw 3 spd,and the mainshaft from the OD tranny.3 and 4 spd Saginaws use the same mainshaft,but the OD shaft is shorter.3 and 4 sp tailhousing interchange,the cases are very similar,but 4 spd gearset reverse won't fit a 3 spd case.Comparing the 3spd OD and 4spd cases,drill one hole by hand,need to build up some weld on the reverse shifter fork so it acts on the a rod to knock the OD out when in reverse.
I've never seen a BW T85 tranny with OD in the common GM imput shaft and bolt pattern,typical Ford tranny.All GM OD's are the Muncie 318 or Saginaw to my understanding.GM did offer the non T85 as a 3 speed option in trucks years ago.
The OD unit from the earlier Muncie transmission looks similar,but won't fit on a Saginaw.
