Inspection of a 904 torqueflite
I wouldn't assume there is a low gearset in that group just because it has that shell with it. It very well could be switched; plus the fact that it was identified as a 904 gearset. Go ahead and think the driveshaft pushes the output shaft forward and that it's a good idea to set the trans up on the output shaft (I don't care who says to) but you are only repeating incorrect information.