Uploading an older datum and projection onto a newer data collector

The company I work for recently purchased a Topcon FC 500 data collector, running MAGNET Field v3.2.1. I am trying to upload an older version of NAD83 to make the data collector compatible with all of our older jobs. I was easily able to move the files around for the older geoids and access them through the edit coordinate system window within the job, but the files that I moved from the older data collectors containing the old datums and projections still seem to be inaccessible through Magnet.

If someone has encountered this same problem, any help would be appreciated.

I believe that I could create a custom datum for NAD83 if someone could give me the specific parameters.

Let me know what you think!