The bottom two steering couplings you pictured are for non-airbag cars. I did not experiment using one of that type in our cars for this swap, but I'd be interested in the results if you do so. Maybe this is the key to prevent the need for grinding the firewall and its covering plate?
The coupling in my airbag car had about 250k miles on it, so the joints were sloppy. When you held the unit horizontally, it would immediately bend under the pull of gravity. Also, the rubber disc was not visibly cracked but you could rotate both halves of the joint probably 30 degrees or more.
The new unit has stiff joints and no articulation of the rubber disc was possible.
If you do use the non-airbag coupling, then make sure it's a new unit. Replacing the rubber disc will be a big improvement on a used unit, but there are still 2 u-joints that will have slop.