Rbrooks45 -
I personally have no experience with the removal of nickle plating from steel. However, if you do a search with
www.google.com you will find there are two ways to do it: (1) with chemicals which are dangerous and require special precautions because of noxious fumes; and, (2) using a reverse electrolysis procedure.
As a suggestion, it might be worth checking with a motorcycle shop that does plating of motorcycle parts. They will probably be familiar with reverse electrolysis since they are experienced with plating motorcycle parts.
And everything written above about the importance of close tolerances is especially important.
Good luck with your project.