If your swapping from drum to disc you will need the proper spindles, & proportioning valve.
Those would be the usual E-bag and the like. Post want adds on any forum that would be likely to have enthusiasts of these trucks.
I would think either rebuild kits or rebuilt parts as well as any other disc brake parts, would be available over the counter at your local parts store.
I have mechanical Aptitude.
I can screw up anything.