As mentioned the hole was cut with a torch, and not very nice.
The opening is offset on the tunnel towards the driver...there are some folks on Steve's Site who have listed the exact dimensions before and images. I also noticed that the original factory paper floor insulation had a 'knock out' for the shifter hole...there were perforated lines showing the exact spot. They used the same paper for both floor shift and column shift cars...of course locating an original one may be difficult. I wonder if repro ones have this feature???
A Super Shifter may require a little massaging to the opening to get the room needed. I installed one ages ago in my first L78 car, a bench seat 70...seems we needed to enlarge the opening. Of course, that was 45 years ago
-wilma