When I had my '65 Fastback, I used a Hurst Super Shifter III with the reverse T-handle to lock out Reverse when needed. can also use the Regular Super Shifter that is more street friendly.
Considering the SS has straight rods (excellent for racing) the entire shifter is offset nearly 4" to the left. I don't think I'd call nearly doubling the size of the hole "a little".
yeah +1 for the competition plus. that is what i used in my 65 fastback.
it never jamed or missed a gear . i used the 70 mustang hurst shift boot and plate and did not have to modify the opening.