Check with Engineered Components Inc. (ECI). They make a kit that is basically a spacer for the spindle, caliper bracket, and hardware. Caliper bracket bolts to the same bolt holes that the backing plate bolted to. Use mid-size GM hubs and rotors if you want Chevy bolt pattern or Aspen/Volare rotors if you want Ford/Plymouth/Dodge bolt pattern. With the spacer pressed onto the spindle, the bearings that come with the hubs and rotors fit the Ford spindle. That's what I have on my '38 Ford pickup, it would be the same kit for your truck.
The rotors on those aren't what most use in thier kits. But most of the kits nowdays use the metric calipers on the 79.
The rotors and calipers I used with the ECI kit came off a '76 Buick Regal, lots of mid size '70s GM rotors and calipers are the same.
In late 77/early 78 there was a big changeover from the bigger calipers to the metrics. Same with rotors. Almost all of them will phisically bolt on the spindles/adapters as the bearings were the same, but the depth of the "disc" varies. Such as a 70-78 Camaro carry the same number as the 70-73 Nova, but the 74 is different. It will bolt on, but the caliper isn't in the right location then.