Are the pins you are referring to the ones that hold the coupler to the factory drive shaft and pinion gear? Someone who has purchased a Mitchell should be able to tell us if the overdrive holds the two different drive shafts located. I suspect you only need to have the coupler pinned to the pinion, but can't verify since I have not installed a Mitchell in a V8 myself.
What exactly did you buy? the gear box only or the entire tube and gear box assembly -- picture?
Yes. And as you are saying, the only way to use two out of four pins , is to mount the coupler to the pinion gear , then just stick the Mitchell drive shaft on the coupler. But , is that good enough for keeping up with the torque?
The coupler takes the torque, make sure the splines are not worn out. The "pins" in the coupler are identified by Ford as rivets. The purpose of riveting the drive shaft to the pinion was to locate the driveshaft front-to-rear in the torque tube.
To my understanding, if the Mitchell assembly locates the rear drive shaft so it cannot slide up and down the torque tube then you don't need to rivet it to the coupler. If the rear drive shaft slides out of the Mitchell unit, then you need to rivet it to the coupler, and slide the Mitchell unit over the rear drive shaft.
Again, the best answer is to get the installation directions supplied with a Mitchell unit.
If you get the instructions then follow them. Those are an expensive unit and they should be installed by the specific instructions. Putting it together thinking it "may be good enough" could be costly.
Aren’t there anyone more out there that got knowledge about the Mitchell Gear Splitter ?