Open-stem galvanized rollers
That later build date matters for rollers specifically. Doors from the mid-to-late 1970s usually shipped with galvanized steel rollers on open stem bearings, not the sealed nylon rollers that became common later. If nobody has touched the hardware since the house was built, those original steel rollers are still doing the work, and they're the loudest, roughest-riding rollers we come across.