I don't think 600 arabesque RDs were ever intended to index, does it have a barrel adjuster on it? If no you are out of luck, if yes you'd think it would work... that's about all I got right now.
__________________
1 Super Record bike, 1 Nuovo Record bike, 1 Pista, 1 Road, 1 Cyclocross/Allrounder, 1 MTB, 1 Touring, 1 Fixed gear