I did a disc brake conversion on my '38 1 ton keeping 6 lugs. I used 78-80 c1500 calipers and 78-80 k1500 rotors.
The master cylinder is a 1 inch bore. I fabricated my caliper brackets out of plywood to get the right shape and positioning then cut them out of steel.
I installed tapered bearings, residual valves, ran new lines and I was good to go or stop.
