Inspection of a 904 torqueflite

CudaFactHackJob said

The driveshaft better never push the output shaft forward. The sun gear can be switched in the low gear shell.

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The op already posted that there is a .010 difference in his measurement by standing it on end. To me that makes Rick Allison recommendation valid. Your driveshaft can absolutely punch that small .010 slop around the snap ring in the tail shaft forward.
What you don't want is to have the output shaft pushing the drums into the pump. That's why there is a spec on the input shaft.
I understand that it can be switched but I have never done it.
My point was that the op correctly identified a low gear set and you questioned him on it as if to say he was not correct.