Remove the shifter and extension housing so you have access to the shift rails .
You can try to place the rails back in neutral position .
If you can't shift it by using a big screwdriver, your gonna have to split the case to find the problem.
I don't know who or if this tranny was rebuilt or just painted bright red .
But from seeing the black silicone instead of gaskets , and the dirty bolts i wouldn't touch it with a 10 foot poll.
I can tell you from experience that tranny is just waiting to fail
And if and when it does there are no hard parts to be found in America.
Japan is your only choice and its gonna be expensive .
There should be an external plugin on the distributor that you can use to power the Tach .
If I remember correctly you should have three wires on the Tach itself . A ground wire , A power wire for the Tach light , And a wire that attaches to the distributor .
The Tach should have come with a...