If I remember correctly I had about an inch of cable or more (the inner cable) once it was all hooked up.
I put the return spring for the throttle pressure on the trans (actually from the lever to the front cooler line) because the lever has some spring to it in it's travel but it doesn't pull the lever all the way forward without an external spring on it.
I really do think you might have yours too tight and that's why it won't shift.
The cable is made to mount under one of the extension housing bolts and pulls the lever to the rear of the car when the throttle opens.
Is this the way yours is?