Yes this sometimes happens with the overdrive boxes.
Here's what I do;
With the tail loose I flip it 180*, then install whatever bolt back in that is closest, but that allows access to the cluster pin.
Now
go to the front of the box and remove the welch plug, then drive the pin out.
Caution!
If the pin will not clear the tailpiece, first I remove the one bolt and turn the tail for max clearance. If the pin still won't clear, then I grind on the tail until it does.
Later, before it goes back together, I make it pretty, then rough it up a bit to sortof match the as-cast parts..
To remove the Welch plug I drill a big hole in it and pry it out with a screwdriver.
There is another option;
You can get a bearing puller and pull the front bearing off the input gear. Then, with the tail loose, you can angle the gear train up, and pull the input gear out of the box. Sometimes the rest goes out the back at the new angle.
But if not, just remove the snapring holding the 3>4 synchronizer on, and pull the assembly out. After that, everything else should go out the back.
However, to reinstall the mainshaft later, the easiest way is to lay the cluster in the bottom, install the input gear, with it's special outter snapring, and with it's brass, then stand the box on it's face with the input gear dropped thru a hole in the bench, then feed the loaded tail in, flipped 180 degrees. Finally, install the cluster pin, rotate the tail into position, secure it, then lift the assembled beast out of the hole in the bench and lay it on it's side, to install the front retainer, and a new welch plug.
Therefore, I use the first method exclusively.
That's how I do it, and I've done a lot of them.
Yes there are other ways.
To make this work easier, the tail usually has to be clearanced for the clusterpin, beforehand, and the gasket lightly glued to the tail..
Happy Hotrodding.
