I agree with Pontiacgp. You can't guess, you must mount the trans and see where the shifter wants to hit the tunnel. Mark it, and cut a small hole at first. Then you can enlarge it as needed. As you work the shifter, you will see where it hits and where to cut more. In my pic, you see a HUGE hole at the rear, because I had previously welded the hump to the tunnel and had to cut the whole mess out.