My CR Cobra has a Richmond Gear 5 speed with a Hurst Competition Plus shifter (I don't recommend this setup and it's the next thing to get swapped out by the way). The shifter mounts to the left side of tailshaft housing and thus sits to the left of the cars centerline. To make room for the shifter in the tunnel, I fabricated a bulge in the tunnel. I seem to recall making some vertical cuts in the fiberglass, using some force to bulge it outward and then fiberglassing the needed bulge shape in place to provide the needed clearance.
Here's a picture of the interior in a finished state. You can see the bulge but it looks fine once covered with carpet and the shifter boot.
I plan to swap out the transmission with a TKX sometime when I get around to it. I anticipate the shifter position will move more to the tunnel center. I may or may not remove the bulge depending on what is involved once the transmission swap is complete.