I have just acquired a Miyata 1000 frameset made in 1982.

I would like to use it with centerpull cantilevers rather than v-brakes, but I'm not sure what I'm doing.

The cantilever cable stops, on both the seatstay brake stop bridge and on the headset spacer thingy, don't have any features for actually holding and stopping brake cable housing.





Is there some specific part intended for this?

Those stops are designed to be used with barrel adjusters. The housing ends at the barrel adjuster, and a nut on the threaded barrel stops the adjuster from falling through the hole in the stop.

See pic, this is a different design but works the same way:
https://velobase.com/CompImages/Small...D2089B6EC.jpeg

1985 Trek 620 by Dave The Golden Boy, on Flickr

IMG_0220 by Dave The Golden Boy, on Flickr

1990 Miyata 1000LT by Dave The Golden Boy, on Flickr