I've turned a few axle flanges down on the lathe so that the guys could run front disks on them. Don't remember all the specs, I just made the axle flanges fit in the disks that were provided.
I've had a pair of 80 front disks hanging on the wall for a couple years meaning to do a rear disk setup on my own CJ5. With 33s, the manual braking was okay (front Waggy D44 w/disks and rear Scout D44 with 11" drums) but with the 35s, "panic braking" is now marginal. My plan is to use the CJ front disks, Caddy calipers (with parking brake stuff.. been sitting on my fridge for 2yrs), whatever soft hoses fit and make my own weld-on brackets. I'd like to go with a Hydrovac booster but may settle on whatever will fit for cheap.
Some of the guys have been swapping Nissan Calipers and Samurai disks onto AMC20 axles. I have the AMC/Nissan pattern in CAD and can cut the caliper brackets out of 3/8" (on my CNC plasma table) if anyone is interested.. Figure $25 shipped for a pair of the brackets. Lead time would be a week or so (basically the next time I get 3/8" on the table).