Nice write up. I finished up my brake swap on my 76 D100. I machined custom aluminum hubs and used 13" Mustang rotors and 2008 up Chevy s1500 calipers. They work great. I recently machined more hubs for my friends 89 D150 and made mounts for Wilwood calipers. He is also using 13" Mustang rotors. When machining the hubs, I accounted for the rotor mounting thickness so my wheels would be in the stock location. They barely clear my 17" Year One ralleys. I will post pics later if I can figure out how.