I am currently doing a disc conversion on my narrow axle Model 20. (80 CJ7). I have all the components and will be documenting this on my site (see sig). Please note I am doing a frame up re-build, so it might be a while before the brakes are road tested. However, I will be able to comment on the fitment and availability of the parts. I was able to find rear calipers from a Nissan 300ZX at my local pick and pull. For both calipers with all brackets, bolts, soft lines, and pretty good shoes (although I will put on new shoes) put me back $32 after core and environmental charges. I picked up brand new rotors (96 Geo Tracker front rotors 2-dr) from AZ for $23/each and built the conversion brakets from 3/8 plate I got from my local scrap yard ($8). The superior 1-pc Axles should be here today. I powder coated the brackets and cleaned and painted the calipers with ceramic caliper paint. I will have an update on how everything fits together with pictures in a few days....
Note: if you print this PDF with your printer set with no options set to resize...ie (do not fit to page), it will print 1:1 to the drawing...meaning you can print, then cut these out for templates. to be sure yours is printing correctly, measure the brake line holder it should be exactly 4" long and 1" wide on the paper.
I built my brackets by using a simple cutting torch and drill press and was able to get everything to fit with just a little grinding.
A local machinist here in town made some 300ZX caliper brackets for me. I got a set for an XJ D44 and a scout D44. The machinist also had a set he made for himself to fit his CJ AMC20. He is thinking about making these and selling them on ebay but has not started yet.