I cut the whole side off from just behind the first bolt hole. I was able to get the anti-pinch rube out, and will duplicate something after I move the bolt hole over to the closest available spot.
I closed off the cut opening with 1/8" plate using 3 pieces. The longest piece fit in the opening very tightly and overlapped the lower plate. I welded as much as I could to the floor. I still have to grind some of the welds as they ended up with some drips in them. Obviously, I'm not a professional welder, but it has good penetration and will look a lot better once I burn up a grinding disc on it. Overall, it seems pretty strong already, but I am going to weld a plate on the inside of the car from the driver's side over the hump to the passenger side to finish it off. I'll have to hammer down part of the sheet metal on the floor and weld up the seam that has the big gap by the old shifter handle base.
I should have plenty of room now! A 518 would still not fit, but a 200R4 sure will! It wasn't that hard or time consuming either. I could finish it up today if I didn't have to go back into the ol' salt mines.
Once I get this cleaned up, I'll start thinking about how to fabricate a bolt-on rear crossmember/transmission mount bracket.