Finally! I found some time to work on the Alfa.
First up, removing the old brake servo. It came out easily, with a minimum of fuss. Before:
Retaining clip:
For whatever reason, the nuts on the new booster used an odd UNC thread pitch. It took us awhile to find the right ones.
I installed the OMP shifter knob [an eBay find]. Unlike the tall Momo part, this one is reasonably sized and sits in a comfortable position.