Is it possible that you just need to put both shifting arms, on the outside of the Tranny, into neutral ?? Hard for me to explain. You have 2 arms that the shift rods go into. IF 1 of those is out of sync, so to speak, it has effectively jammed the other shifter. Try to work each one separately, to find a "Neutral" position.
DO NOT USE FORCE
Very common on old worn tranny shifters, back in my day.
DO NOT USE FORCE
Very common on old worn tranny shifters, back in my day.