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

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!