I'm not sure Synchro era (late 80's) indexing was the same as Ergo, so I can't give you a definitive answer; but:
I do know I never got my 80's Chorus 7s derailleur (the one with the A/B adjustment) to play very well with my 8s Ergo. It was just never quite right. Everything worked much cleaner & quieter with a 90's era Chorus rear derailleur. YMMV.
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