nomad; That torque tube seal is made buy Bruces Rod Shop, 6721 Klein Cemetery Rd, Spring, TX 77379, phone 281-376-5932. It is used to prevent the gear oil in the rear end from draining into the torque tube, especially on cars that have a "rake". Having a "rake" drains your banjo of gear oil. Over the years, that gear oil will also dissolve the rubber encasing the torque tube center bearing. It turns to mush as shown below. I installed that torque tube seal on my 40 in 2017 as my 40 is severely "raked". Be sure to save that piece as it is custom made and others may need it. It appears that you have the later version. If you do decide to use that seal, the instructions say to install an axel tube vent. The one shown in photo 6 below is home made. Picture 5 is a NOS torque tube center bearing. I have seen an aftermarket seal available on Fordbarn by "Skip".
https://www.jalopyjournal.com/forum/...stion.1023765/
Here's more info.
https://www.google.com/search?q=torq...hrome&ie=UTF-8
https://www.fordbarn.com/forum/showt...center+bearing