My 80s Raleigh also has a diving bell cable stop along the chainstay. The frame did come with the correctly sized stepdown ferrule to fit in the cable stop, only problem is that it doesn't fit modern index derailleur housing, the housing is too fat. I 'solved' the problem by using another stepdown ferrule and another regular ferrule. Indexes fine so...maybe I don't mess with it.

And I've also got to figure out the appropriate stepdown for CLB brakes, the ferrule and housing is too large to fit.