I'm going to guess that the leak is at the axle flange gasket, not the inner seal of the hub. That's a pretty simple fix, and that gasket fits 3/4 and some 1 ton trucks for at least 30 years, up to at least the mid-1970s or newer. Any local parts store should have one in stock, or at least be able to order it.
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
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