Suggestion on your trans shifter hole - cut it in the shape of a rectangle, large enough to the rear to allow the transmission to slide back about 4". Then use an aluminum plate with a round hole to cover the void. You can rivet or screw it to the tunnel
If you ever have to pull the transmission, you need to be able to slide it back far enough to clear the bellhousing. You need to be able to pull the transmission back far enough that the input shaft disengages from the clutch splines, allowing it to then tip on an angle. If you just have the round hole, it won't move back far enough, you'll then have to pull the engine to get the transmission out.
Paul