Hi Gary-
You are absolutely on track- those rod ends you have from the 1929 President (disassembled) seem to be a match- the "housing" or body of the rod end is formed steel (not cast like other parts) and the thread sizes you estimate are what I measure as well- 9/16-18UNF on the ball end and 3/4-16 on the rod end.
Seeing yours completely apart and cleaned, along with the great article you provided (thank you), gives me motivation to disassemble this one and see if it can be refurbished.
To answer an earlier question, these are the outer tie rod end that mounts the steering tie rod to the front spindles (picture attached). The tie rod itself is also as Gary describes, larger diameter main tube with each end tapered and swaged to the smaller, threaded diameter. The tie rod on this vehicle is straight, so even if I had to have a new one fabricated with different thread sizes, it might be somewhat straightforward.
My preference is to use as similar to original parts as I can, so I'm interested in buying the President end parts from you (the pair). I'll send you a direct message with contact details.
Once I get through this, I'll post up some findings and my ultimate solution. So far, you have all been very helpful and encouraging, I sincerely appreciate your time and information!
Bill