'71 was the first year for disk brakes.
Unless its just come out, there is no commercial kit that puts disk brakes on the front of a 3/4-ton that preserves the 8-lug hubs and towing capacity.
Several people have managed to make a conversion and your best bet is to search out pictures of those and study what they did. Its much easier to do if you do NOT need to keep the original wheels.
Basically you find a rotor that will adapt to your hub, then choose a caliper and build a bracket to mount the caliper in the right place. Easy enough....
After researching it a bit I ended up deciding to go with an IFS swap instead, but the reasons weren't really the brakes, but some of the other problems IFS solved.
