Hi Noah,
Excuses me for the late reply.
The 6500 are 2 type of mechanism deck: with two motors (first version) and one motor (last version).
First, see your 6500 if 1 or 2 motors (if 2 motors, one is up and other is back). If one motor, the deck looks like this image (sorry, i'm not a great artiste)

The Beocenter 9000 is a version with 2 motors, the cables and plugs is not same for Beocord 6500. But the head is same.
I do not know for BeoCenter 9500, I have not the technical documentation. But the same rotary head is used and
I think if the versions are the same like your 6500 (one or two motors), it should go, except perhaps fixing problems and cable/plug lenght.
Avant c'était pas mal, aussi bien qu'aujourd'hui, mais en plus vieux 