I know there are a couple disc brake kits for the 3/4 & 1 ton trucks, though sadly they won't work with the front hubs on dually trucks.

1949 Chevy 3100 (In the family since new)
1955.5 Chevy 3100 - in the DITY Gallery - (Dad's truck)
1955 Chevy 6500 - in Big Bolts - (Possible parts truck?)
1958 Chevy 3800 w/9 ft bed - in Project Journals - (Current project)
1959 Chevy Spartan 10400 - in Big Bolts