OK, I'm going to say it. I have no intention of hurting anyone's feelings.
If someone gave me a complete R10 overdrive transmission, I would not install it in my truck. Parts are hard to find, and ones in good condition are hard to find as well.
Another reason not to go that way is, since you will be going away from stock, why not go with a far superior option of a T-5. They are the ultimate upgrade for a Stovebolt engine. Another bonus with the T-5 is getting away from the problematic 3 on the tree shifter.
Those R10 transmissions are somewhat in demand, so if someone gave me one, I could easily sell it for more than what a junkyard T-5 goes for.
Carl
