49 to 52 Olds should fit the same, and all of those are 6volt with the smaller ring gear on the flywheel. 53 should also fit because it is a small gear type, but is a 12volt. 54 and newer won't work because their flywheel gear is bigger diameter. You can buy a new modern style mini-starter from Goatroper02 on hamb, who also can be found on the web as "Ross racing engines"