Should not be a problem changing out either older Bottom Bracket or Hub sealed bearing cartridges.
On older hubs, in place of the cone, there is usually a "cone-like" flanged sleeve which passes through inner opening of the bearing. I don't have a good break-down view, but this Sansin hub is from 1985 and still spins wonderfully smooth. The cartridge bearing insert resting in the hub shell would be easy to replace.
... here is the main page for this image:
http://www.flickr.com/photos/strongl...7605576341958/
Here is a simple, very inexpensive, and wonderful little bearing puller tool which can be used for removing hub bearing inserts -
and dust covers too! It is only 55 mm. long, probably still sells for little more than $5, and should last forever despite the cheap appearance. These can be ordered through most bike shops from the big wholesale bike parts distributors, or check online as well. Worth every penny.
See more images showing how it can also be used for dust cover removal in the following set:
http://www.flickr.com/photos/strongl...57603240644450
Many older cartridge-style bottom brackets used very simple bearing inserts which simply snap onto a flat section of the spindle - right where there would otherwise be a bearing race on more conventional axles. And the outer dimensions of the cartridges just sat on the flat sections in the cups. Here is a Stronglight version from the late 1970s. The original SKF bearings seen here are still available - as are many other modern cartridges which still have the exact same dimensions. As these bottom brackets gradually evolved, they would eventually acquire metal sleeves which gave an appearance of more modern sealed bearing units. But, initially those were really just fancy "crud-guards" - much like the earlier plastic spindle covers for cup and cone style BB sets:
... original image page:
http://www.flickr.com/photos/stronglight/3792936806/