The Rusty Hope directions were pretty clear to me...
Basically, you remove all the original brake stuff off your axle. If I remember right (its been a very long time) there are two spindles Dodge used on the truck beam axle, one was a 3 bolt, and the other was a 4 bolt. He can help you get the right kit. You bolt the caliper brackets he provides to your spindles (you may have to enlarge and tap out a couple of the original holes in the spindle (on the cars you did, don't remember about the trucks). Then you use the bolts he provides and bolt the caliper brackets to your spindles. You slip the bearing spacer and seat lip (its a machined part) over the spindle where the drum/rotor runs, and push it back to seat against the back of the spindle (a light taping may be required). Then you pretty much buy and install the rotors with new bearings and seals, calipers, brake pads, and hoses he provides part numbers for.

The most difficult part (which you may not have to do) is drill out a couple existing bolt holes to the next bigger size and tap the threads in the holes. Past that, its pretty much a disc brake job. Gene