One wire lock-up, 4 spd automatic w overdrive into A-body.
Test fit the engine/trans and as Treblic predicted, the cut is in the exact spot his was. What a pleasure to lower the car onto the engine/trans rather than stuff it in through the hood opening. Way faster too.
Now I have to decide if I want to cut out the corner and flip it around using it to fill in the hole, or (Plan B) cut the entire corner off and weld a flat plate back on it to cover the hole plus weld another flat plat on the inside of the floor extending a few inches past the newly cutaway section of the car to create a layered effect.
I guess I will see how well the part I cut off fits back into the hole in the crossmember. If it doesn't come out fitting well, I will go to plan B. I way weld a plate inside the car just as an extra strengthening attempt. I f done right, it should be stronger than it was when I started.
I am going to move one of the crossmember bolt holes over about an inch, as it is right inside the area that has to be cut. I want to re-use the inner tube, so I'll drill and cut carefully.