Disc options for 73-76 drum spindle???

Hi all. What disc options are out there for the 73 to 76 drum spindles? AR Engineering doesn't show their swaps on their web site anymore, are there other options? What other calipers can be used and who does the mounts? The cheaper the better.
I'd think it would be easy to make an adaptor plate to mount any 2/4/6 piston set up, but I'd rather something tried and tested.