I had the same problem. By taking off the shifter boot and pin like "Massey Driver" suggested, and also taking out the filler plug (right beside the shifter on my 65) I was able to free up the linkage by putting a screw driver in and wiggling the linkage while wiggling the shifter. Good luck.
P.S. I'm told if you push down on the shifter when changing gears this is less likely to occur)