727 - Driveshaft Jammed All The Way In

Rear bushing is likely fine. You can see in the photos the slip yoke has a dirty area where the seal never rode against. So the output shaft was bottomed out inside the slip yoke, away from the rear bushing.

Editing to add, there is a chance the trans was fine and the previous owner just put an ugly slip yoke in there with a driveshaft that was too long. So the rust and dirty fluid in the rear did not get anywhere else. But chances always bite me in the ***.