Most of the bearing cones and cups I've worked with have a number stamped into them that can be cross referenced between various manufacturers. Unless the bearing is totally destroyed, the numbers on the old parts usually survive. A good set of dial or digital calipers and maybe an inside micrometer can also come in handy, using a bearing and/or seal manufacturer's progressive size charts. The obsolete rear wheel bearings with the barrel-shaped rollers are extremely scarce and e$$$$pensive, but sometimes a conventional tapered roller bearing with the same dimensions can be substituted.
Jerry
