My 64 Barracuda 4 sp appears to be hung-up between gears. Anyone out there know how to unhang it without taking it apart?

 

Not knowing what you have done so far, the first thing I would do is disconnect all three rods and center the 1-4 levers to neutral it and see if it turns at the output shaft. If not operate the reverse lever and see if it is stuck in reverse. The reverse mechanism can break or lose the detent ball and have that jam in the gears.

 

We need more details. It doesn't roll back and forth and is locked in place?
Without knowing any better I could say you chewed up your spider gears in your rear end?