While restoring my 69Z, Norwood 05A car (built first week of May), I discovered that my shift hole was rough cut with a torch. (PS: sharing the plant and build date of our cars helps to define common assembly plant practices at the time our cars were assembled
Attached are several pic's of mine shifter hole. Notice the original caulk outline for the hole vs. the cut hole.
You may be able to enlarge and print these pictures to approximate a scale (i.e. 1/4" = 1"), to layout your new floor board. I did not think to document the location of the hole at the time of my restoration. As recommended in this discussion, use the shifter boot retainer plate as a template. Do not cut the hole any larger that the ID profile of the plate to leave sheet metal for the screws that secure the plate. Go conservative. Notice how much smaller the hole is vs. the caulk outline.
One other option: mock up your trans and cross member, with the shifter attached without the shift handle, and then mark the underside with a Sharpie, to find the centerline location for the shifter handle. Drill a hole from this point to fine the hole center. If you have a 4-speed console, locate the complete assembly, with the shifter tunnel in place, to help locate the approx. hole center from the top side. The front lower edge of the console measures approx. 11-1/2” down from the inner firewall.
Good luck with your project.