David, so I checked and it seems tremec still uses the same input shaft bearing retainer on tko and tkx input shafts. The retainer od you are looking for I assume is this one ?
https://ad4062394301f5213879-385273f...3_af80b75e.jpg
I used a McLeod choke ring ( some call it reducer ring) to allow my Ford OeM bell housing to work with the tko.
I have the tko retainer in my shop and can measure it and report back.