Bolt on Disk brake conversion for 66 Valiant

Doesn't surprise me a bit. I just don't like seeing aluminum mixed with steel and/or cast iron and then adding heat. Dissimilar metals don't usually like to play nicely together.

They're floating rotors anyway, with the rotors secured to the hubs by the lug nuts. All the 2 piece rotors in the fancy aftermarket kits like Baer, Wilwood etc are all cast iron rotors bolted directly to aluminum hubs, and those are fixed rotors.

My ford work truck has cast alum upper control arms

Exactly. From an engineering perspective an aluminum control arm is a more difficult part to design, especially the cast kind. Much larger lever arms, multiple fixed and pivoting points, etc. All kinds of modern vehicles use them though. Probably more use aluminum UCA's and hubs than not.

Sounds good and I like doing business with them anyway I will try to get them on the phone the reduced staff during this covid BS .

I know Cass was closed for the holidays. Not sure how much the "staff" thing effects him, I honestly don't think anyone other than Cass has answered the phone when I've called.