The early first gen Campy 9 sp RD's are indexed the same as 8 sp RD's. That's why first gen 9sp RD's are the way to go when the 8 sp RD's can't be found for less than an arm or a leg.

My Record/Chorus 8 sp group has a Chorus 9 sp RD.

EDIT: Campy 8 sp Ergo's work well with some 7 sp freewheels as well. You just have a dead click.