Gary,
Wow, I guess since you have owned the truck since 1961 you certainly do know its history pretty well. Most of us don't have such a clear provenance, but then you are limited in blaming past owners for things that are messed up.
The torque tube transmissions look much more difficult to install than open driveshaft versions.
Have you ever taken out your shifter lever? It is very easy and makes filling the transmission with oil a breeze. The 140 GL-1 should help some with the leaks but shifting will be difficult at first when cold. I would still fill to a level approximately 1/2 below the fill plug. I hope it works for you.
Paul
