Thanks for the link. That explains a lot. My Oakie bushing has a leather oil seal with stamping M-101 and National Mach WKS INC. Looks like 1.5" OD and will probably be replaceable with a modern part unlike my GM original oil seal which was a Chicago Rawhide (CR) 10647.
My idea is to cut the Oakie bushing and use the part removed as a seal holder. I'm afraid if I ever install a complete press fit Oakie bushing it will never drive out again and I want to have this capability. I have a 54 Hydramatic torque tube and the new seal will have to keep transmission fluid and oil from the rear axle from combining. The original GM seal has worn the torque tube shaft enough to be a problem for sealing. The new seal will be in a different position and hopefully will seal better.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."