The inverted flares may be too small for a flare type seal. I've used the soft metal Voi-Shan conical seals but they are generally for AN 37 degree and SAE 45 degree type flares. I'm not sure if they will work on the Eaton or Weatherhead inverted types. They are soft copper so they conform to the flared fittings well. If one is close to the right size, it certainly wouldn't hurt to try one.
Having been an owner of a 1964 Thunderbird for a long time in my earlier years, I can say that I never had more problems with any other hydraulic pump than I did with the Eaton type. That was actually one of the reasons I sold the car. The steering shared the pump with the windshield wiper motor and that system was always giving me some problem. I shy away from the complicated cars now days. A hobby car should be easy to repair/maintain and be fairly reliable.