power steering problems

I have a 1974 duster 360 with power steering. Originally was a 6 cly and the power steering was on it originally. Every since I have owned it (14 yrs) the steering wheel will automatically turn to the right unless You hold the steering wheel in place. I have replaced the power steering pump, the pressure regulator valve on top of the steering sector. still the same problem. I'm guessing the regulator valve on top of the steering sector is allowing too much pressure. Do I need to increase the spring pressure on the check ball or less pressure? I thought the pitman arm might be off center but no matter where you set the steering wheel it will go to the right passenger side all the way till it hits the stop. I am willing to convert it to manual steering' but I need some input as to what parts I need to change out. Just rebuilt all the rubber in the front suspension. I sure would like some expert input on this problem.

Thanks All