Find out what the diameter is of your centerpost. Then find relevant rigs today, or look for older docks that fit posts that size. For example, the CP Steadicam™ Models III, IIIA and EFP all used 1.5" centerposts. A few newer rigs do as well. You may find a manufacturer who makes a dock now that can accommodate your post size.
You will need to make sure that the docking bracket has a stud on it that is identical in diameter to the arm post diameter. However, if you find a great dock for your post size and it lacks the proper diameter stud, a good machinist can turn one out for you.
Best of luck, and welcome !
Peter Abraham, S.O.C.