First of all, if your Power Steering system is old, the chances of getting it to not leak is minimal.
The Seals, Get hard, do not scrb the sliding parts, oil will continue to by pass these seals, gaskets, etc.
Hoses, Same, they dry out crack, then the actuation of the unit further deteriorates them.
As far as the Fix, You can send these out to be rebuilt, having the number correct originals back, you can buy a new cylinder, Hoses, and have a new Control Body installed.
Several combinations to fix the problem.
Achieving a leak free , excellent system is simply a matter of doing one of the above.
Dan
Classic Mustang Disc Brake Conversions and Power Steering