Here is what I did. I had the axle shafts turned down slightly. (you can do this with a grinder if someone spins the axle for you. Then I used CJ-5 rotors, I think it was 70's era. After grinding on the shaft the hat of the rotor fit down flush on the wheel mounting surface. Using the lug nuts to hold the rotor in place makes sure the run-out is acceptable. I used 3 5/16" countersink allen head bolts, drilled and tapped the axle shaft, and countersunk the rotor. Once the wheel is on these, bolts really dont do anything, but are required since the rotor holes are larger than the wheel studs.
On the backing plate, I cut the center out of the old drum backing plate, it is used as a shim and you need to keep it, or make a new shim. I used a chevy 1/2 ton 4x4 front caliper bracket, cut beween 2 holes so the bracket could be put on without removal of shaft and bearings. For this to fit my bolt pattern I had to englarge the holes just enough to get the bolts through. If your holes are to far off you may want to drill new holes.
Once rotor and caliper mount is on, I bolted on a chevy 1/2 ton 4x4 rotor and hooked up the lines.
You can also sub in a caddy caliper if you want and e-brake.