That looks like a cassette hub due to the thicker cross-section closest to DS.

The RD is first generation superbe from the 70s, and I wouldn’t expect it to index correctly with the last generation superbe pro accushift index shifters from the late-80s/early-90s. However, the index shifters were compatible with some contemporary sprint RDs. This might be the biggest clue.

Make sure the shifters were assembled correctly, with all washers and spacers in the correct order and orientation. Insufficient ability to tighten might indicate a missing washer. I have the prior generation superbe pro shifters and they have a lot of bits.

Edit: Just saw your post above and yes, friction should be fine with all components there.