They do get welded to the axle tube. The narrow end fits about half way around the axle in board of the flange where the axle bearing rides. The Alfa hubs are pretty deep, which I wanted for clearing my 13 inch minilights, but they set in so far that a bracket that would bolt to the axle flange is more than I want to make. The weld on bracket is simple.

The caliper slide [float?] will bolt to the wide end of the bracket once I figure out how to mark where the bolt holes go. Then it is down to figuring out how to make the park brake work and I am looking at Lokar for cables.

Do not plan on using a dust shield at this time. I will use a proportioning valve and am thinking to go with one from a Volvo but then might break down and buy a Wilwood.