I know when I did mine I cut out the bare minimum of what had to be cut, and it was still quite a bit. Since it was my daily driver I had to mount the seats back in and drive it. I did not notice any flex at all with the tunnel cut out. Until I got the tunnel back in I just put a cut out section of my plastic inner fender (since I dont run fenders lol) over the U-joint. As far as what had to be cut out, there were some areas where it would not be a whole lot, but there are a few where the housing juts out and you need to make the tunnel go wider. One area I know was on the front seat mounts. I had to cut a notch out right at the inside adge of the front mount, bend the tunnel out more, and then reweld them to each other. From what I remember, if you didn't go for a true flat belly, but setled for 2 or 3 inches of lift, you would have to cut out ALOT less. I have a single case and I am pretty sure I could have got out 3 inches of lift by only cutting the hole where the shift boot mounts a little larger. Another thing to watch out for is the speedo cable. I notched my floor pan for it, and it still over flexed and broke after 20 or so miles, so you might want to consider taking a large notch that allows the cable to flow naturally instead of forcing anything. I hope that helps.
