I bought a T-96 with overdrive set from kaiserwillys.com and a local transmission shop just finished going through mine & installing the gaskets & seals yesterday. No road test till at least spring.
First off, the rear seal is a modern single lip design, not the OEM type wide seal housing with the inner single lip & felt wiper ring at the rear. Probably nothing wrong with the new one but I hunted down an OEM type & left it up to the re-builder, he preferred the OEM type.
I also had them check the thickness of the solenoid gasket which checked out same as OEM. A manual I bought said some modern gasket sets have thinner gaskets and can cause the solenoid to chatter.
Manual is " The Official Guide To The Borg-Warner R-10 and R-11 Overdrive" by Randy Rundle. Seems to be mostly a reprint of the Warner Gear OD manual but with a few tips like the gasket issue and how far to NOT drive the rear seal in. $15 from Jeepsterman in NJ as well as a rebuilt solenoid for $165 with core exchange.
Can't find who I bought the ($30) OEM type rear seal from but jeepsterman might have them.
Here's an overpriced one on ebay
https://www.ebay.com/itm/NOS-1935-1965-Mopar-Kaiser-Studebaker-Hudson-Willys-Transmission-Rear-Oil-Seal/302184051299?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m1438.l2649Edit: I brought the Warner Gear manual, the Official Guide and copied pages from the Willys manual to the shop and they said it helped a lot. Got turned down 3 times due to the OD unit before finding a shop (with an old enough owner) through word of mouth.