Weld on disc brake bracket 

The caliper is the '75 Chevy 3/4 ton(12.5" rotor diameter), it is very easy to find and it is cheap to buy. The rotor will depend on your application, since these calipers are floaters they will go on just about any vented rotor. This is the cleanest way to build an axle, cut off that old drum flange and weld on the bracket, no bolts to check on, lighter weight, easy mounting.