Unfortunately the FSDOs do not really have the answer. A couple of o points to emphasise:
A 61.75 certificate has the Type Rating annotated as Z/, whereas the full ATP is annotated as A/. The rating is effectively meaningless.
As stated earl
MarkerInbound , you need to contact a Training Center. They know what they are approved to offer, and are the gatekeepers to the process.
Yes, there is a Systems and technical training part, but this is no more than you would do on an annual refresher. This is typically completed online.
Good luck.