My 65 Ranchero had a 58 but it was not a posi. My 67 mustang was over 59 and it was not posi either.
I think the only one with a 58 with posi was the early Bronco, if you want a ford rear end.
You may also get lucky by checking the early AMC Jeep or truck styles for posi units.
But really those could have about anything in them from Ford, GM and Dodge