This is the only tree we own that some folks call about sometimes to
inquire on it's status. Some sort of registry?

Hmm, don't know if you are in it but there is some kind of census at:
http://www.bartramsgarden.org/frankl...nsus_info.html

I don't know, do the people calling seem to know anything about how to
keep it healthy? Or are they part of a tree organization which might?

My Dad who knows a lot more than I said Drill it and put a rod with
treads thru it.

You'll probably get differing opinions, and I'm certainly not enough
of a tree expert to even say which opinions are right.