A727 Torqueflite questions (for gurus only lol)

Lefty71 said
I'm working on a '78. Keeping in mind that spline angles have changed...... the question in my head is; if the rear planetary ring gear stays with the correct output shaft, then can only the planetary itself be changed ( since it only needs to match up to the rear drum)?? Or can those parts not mix-n-match?? Not talking about the front planetary here at all.
TIA, Lefty71

The spline angle on the output shaft that's different for different years engages into the front planetary, not the rear. The rear planetary is driven by the ring gear and where that ring gear slips on the output shaft, I believe, is the same on all years