centering power steering box?

Im working on a 65 plymouth. I had to change the top of the power steering box where the hoses bolt or slide on because some past owner put a crack in the cast iron. I have a used piece and bought new o rings bolted it on and when i started the car the steering wheel spun and it was at full turn to the left. Drivers side. It seemed to me years ago that the holes were slotted and you moved the piece to center the box. neither the part i took off or the new old one was slotted. Does any one know how to center it or what i did wrong? Thanks for any help.